snow-flakes from the upper regions of the air.
snow-flakes from the upper regions of the air.
snow-flakes from the middle regions of the air.
snow-flakes from the middle regions of the air.
Snow-flakes from the Lower Regions of the Air.
Snow-flakes from the Lower Regions of the Air.
Note the gradual progression from solid to feathery forms, and especially that every elaboration maintains the six-pointed crystal type.
Courtesy of J. Wilson Bentley.
"Sure!" said several of the boys, and one added, "Mother often makes it."
"How does she make it?" queried the Forecaster.
"Melts up some sugar and water and, as when it begins to cool off, she hangs a string in the middle of the pot and the sugar settles on that."
"It settles in regular shapes, doesn't it?"
"Yes."
"Well, those are crystals. When water cools into ice, boys, it does the same thing. Haven't you sometimes seen, after a cold night, a lot of needles shooting out from the sides from a puddle?"
"Yes, sir, often."
"Those are all six-sided crystals. Frost on the window pane is made in the same way. All those designs that look like lace work or trees or ferns are six-sided crystals produced by water-vapor, in the air, cooling and crystallizing on the cold glass. Ice crystals grow from each other quite readily. This is called twinning."
"But why are they always so regular?"
The Forecaster shook his head.
"You're always expecting everything to be regular, Ross," he said. "They're not regular at all. There are thousands of different forms. The United States is fortunate in having one man who's the world's expert on snow crystals, and he examines and photographs thousands every year and adds, perhaps, two or three new examples each season."
"Who's that, sir?" asked Fred.
"Wilson A. Bentley, of Jericho, Vermont," the Forecaster answered. "He's made thousands of photographs of snow crystals through a microscope. What's more, he's done it for the love of the work. Why don't you send him a copy of theReview, Fred? I'm sure he'd like to see it. Perhaps he might send you some prints of his snow crystals. He'd appreciate a plate of Cæsar's sunsets and Ralph's clouds, I'm sure."
"I'll send them to him right away," the editor answered.
"Why is it," queried Anton, "that when snow-flakes fall slowly and only a few of them at a time, they are big, but when there's a heavy snow-storm the flakes are small?"
"Because they are manufactured in different layers of the air," the Forecaster answered, "inthe upper air, eight or ten miles up, where the faintest cirrus clouds are, they are not flakes at all, but tiny needle-like crystals, called spicules. In the depth of the Arctic winter, near the North Pole and especially on the Greenland ice-cap—one of the coldest regions of the world—the wind is full of these spicules, which one can't very well call snow.
"Snow-flakes that come from the cold regions of the air, three or four miles high, generally have a solid form. All, of course, show the six-sided form of the snow crystals. Being smaller and heavier in proportion to their surface they fall more quickly. In the layers of the atmosphere, one or two miles high, where the air is not as cold and where the content of water vapor is higher, the flakes have more opportunity to grow as they slowly sink through the air. Snow-flakes that have been formed only a short distance above the ground become large and feathery, the kind of which northern peoples say that 'the old woman of the sky is plucking her geese.'"
"I suppose, in the northern part of the country, sir," Ralph suggested, "snow has to be measured, as well as rain."
"Certainly," the Forecaster answered, "otherwise we wouldn't be able to tell the precipitation of a region at all. There is a regular instrument for it, called a shielded snow-gauge. This is like a rain-gauge, boys, only it stands ten or twenty feet above the ground, to avoid surface drifting. The snow caught is melted and expressed as so many inches of precipitation. Sometimes the depth of snow is measured by thrusting a measuring stick down to the ground.
"Of course, that's not nearly all that the Weather Bureau has to do with snow. In the northern states, especially of the Pacific Coast, snow surveys are of great importance. The Weather Bureau often sends men to determine the amount of snow that has fallen over a given area, in order to find out how much water may be expected. This is needed in flood forecasts and irrigation projects. Some of our men, boys, can tell you thrilling tales of their expeditions on snow-shoes up snow-covered slopes where there is never a trail.
"Railroads whose tracks run through the regions of heaviest snowfall build snowsheds to keep their lines from being buried in avalanches, and these sheds are built to withstand pressures calculated by the Weather Bureau. Where drifting occurs and the railroad tracks are being covered with the drifting snow, it is the combined snow and wind records of the Weather Bureau which form the basis for the work of the rotary-snow-plow.
"Even so, boys, the value of the work of the Weather Bureau in snow surveys is very small compared with the importance of frost warnings. These save the country tens of millions of dollars every year, especially in the fruit sections."
"You mean by smoking them?" queried Ross. "Father heard about that a couple of years ago and bought a lot of fire-pots for his orchard."
"How did he succeed?" asked the Forecaster.
"He didn't succeed at all," the boy answered. "There were only two bad frosts that spring, and both times the evening before had been so warm that no one suspected that there would be frost before morning. The one night that he did start the fires, it turned warm towards midnight and we wouldn't have needed the fires any way. Old Jed Tighe, who's got the biggest fruit farm here, has made fun of Father's fire-pots ever since."
"Now, if your father had received the Weather Bureau's frost warnings in advance," the Forecaster said, "he wouldn't have wasted fuel on thenight that there wasn't a frost and he wouldn't have let his crop freeze on the nights that the temperature really did drop below the danger point. For example, boys, if the League of the Weather had been in existence at that time and could have given good frost warnings, all that crop would have been saved, wouldn't it?"
"Yes, sir," said the boys, "it would."
"Of course," the Forecaster continued, "a really progressive fruit-grower ought to make himself partly independent of the Weather Bureau. He can put up frost-alarm thermometers."
"What are they, sir?" asked Anton.
"They're thermometers with an electrical attachment, something on the principle of the thermostat, which you see nowadays in big buildings. A thermostat is electrically connected with a tiny lever, and when the air of a room gets to a certain heat, the increasing temperature operates a lever and closes the steam pipe which brings the heat. When the temperature falls below a certain point, the lever is released and the steam rises again. The same principle is used as a fire alarm. When the air inside a building rises to a point hotter than it could naturally do, it operates a lever which rings an alarm bell. The frost thermometer acts exactly on the same principle. When the temperature of the air, near a fruit orchard, falls to within three or four degrees of the point at which the fruit will be harmed, the fall of the mercury breaks an electric circuit which starts an alarm bell ringing in the owner's house, perhaps a half mile away."
Ringing the Frost Alarm.
Ringing the Frost Alarm.
Thermometer with electric attachment which wakes the neighborhood when the grip of a cold wave menaces ruin to a fruit crop.
Courtesy of U.S. Weather Bureau.
"I've been wondering," began Anton in his meditative way, "whether it wouldn't cost more to heat all the out-of-doors than it would be to lose some of the fruit."
"You haven't got the idea of it at all," the weather expert said briskly. "It's got nothing to do with heating the whole of out-of-doors."
"Then what are the fires for?"
"Just to heat a very small section of the air on the ground. Don't forget, boys, that a fruit tree ten feet high may have all the fruit on its lower branches, up to five or six feet, absolutely killed off, while the top branches are unharmed."
"How's that?" queried Ross in surprise. "I thought frost came down from on top, and that the higher up you went the colder it would be."
"Not at all," the weather expert answered. "Frost comes from down below. When the air is still and clear, the earth loses heat by radiation. The heat goes up and up and through the air to higher levels, the cold earth cooling the air below. Therefore, on a frosty night, in a region where frosts are rare, or at a time of year when frosts are few, a still clear night will cause a belt of cold air perhaps only a few inches in depth, perhaps ten or twenty feet in height, this belt being several degrees colder than the air overhead.
"Now, Ross, you can see that to light huge fires, with the intention of warming up all the air, would be foolish and unnecessary. All that is needful is to heat this lower cold belt of air, a few feet in depth, and only to heat it the three or four degrees necessary to bring it to the warmth of the air above."
"But suppose a wind comes up and blows the heat away?" asked Anton.
The Forecaster smiled at the question.
"If a wind comes up," he answered, "you wouldn't need to use any heat at all, because the wind would mix the warmer air overhead with the cooler air below and there couldn't be any killing frost."
"But doesn't it cost an awful lot?"
"It costs less than to lose your crop," theweather expert replied. "Usually you can figure that a frosty night will take a gallon of oil per tree, or from twenty to twenty-five cents. In a fruit growing section a grower is unlikely to have more than four or five still, freezing nights a year when his crop may be ruined by frost, so that he will spend a dollar or so per tree in protecting his orchard. As there are few fruit trees which bring in a profit of less than ten dollars during the season, and some a great deal more—according to the nature of the crop—the proportionate expense of heating is small compared with the amount of fruit saved."
"Then you think that heating an orchard will save the fruit?"
"Absolutely without any question," the weather expert answered. "And, if the fruit-grower will keep in close touch with the Weather Bureau, he will know when precautions are necessary. Of course, boys, it's especially important for this work that there are a number of co-operative observers, because frost is not a widespread general phenomenon. You could have a fearful killing frost down in the hollow where Anton's house is, or in the low ground near your house, Ross, and still Tom's place, on that little hill, wouldbe quite safe. One of the things that the League of the Weather ought to be able to do this winter and spring is to see that frost is fought. Even when your fathers haven't got regular oil-pots, boys, a few smudges with heavy smoke, drifting over the orchards or the truck fields, if started early enough in the evening may check a freeze."
"Why, sir?" asked Ross. "Smoke isn't hot."
"No, my boy. But you remember that I told you that the cold was caused by the radiation of heat from the earth escaping into the air and through it. If there's a steady layer of smoke, like a blanket, floating across the land, the heat radiating from the earth will not have a chance to escape to the upper air. It will stay in the lower layer of the air and thus keep it from dropping to the killing temperatures of a true freeze. That's what the Indians of the pueblos used to do."
In the mild winters and early springs of Issaquena County, there seemed little reason for the boys of the League to trouble themselves with frost warnings, but, at the Forecaster's urgency, the boys kept wide awake for it. It happened, though, that the lads had talked so much about their frost protection plans that several of thefarmers decided to get some oil-burning fire-pots for use that spring, in the event of a freeze. Jed Tighe, however, one of the few people of the neighborhood who had shown but a perfunctory interest in the League, laughed to scorn the idea of buying the fire-pots, as Fred had suggested in a recent issue of theReview. Even Jed Tighe read the little sheet every week, in spite of his alleged scornfulness.
One afternoon, when Ross was over at the club-house, where he spent so much of his spare time, Anton pointed out that the conditions were ripe for a killing frost.
"The hottest to-day was sixty-two degrees," he said, "and you remember Mr. Levin told us that one wasn't ever safe unless the maximum was sixty-four. There's not a cloud in the sky anywhere and there's practically no wind, and what there is, Tom told me over Bob's wireless, is from the northwest, and that's the worst quarter. I was just going to take the dew-point when you came in."
"Let's do it now, Anton," said Ross. "Got the cup?"
For answer the crippled lad took down from the shelf a small tin mug. It was already brightand shining, but he polished it until it looked like silver.
"I've got the jug of ice-water ready," he said.
Pouring some tap water into the cup, and filling it about one third full, he began to stir it round and round with a thermometer. The mercury in the tube quickly dropped, until it read 50°, showing the temperature of the water.
"Now, Ross," said Anton, "pour in the ice-water slowly."
Ross picked up the pitcher and began to let the water trickle in a tiny stream into the bright tin cup. Anton went on stirring.
Steadily the mercury descended in the tube as the water in the cup grew colder and colder. Ross poured in more and more slowly. Then suddenly, quite suddenly, while both boys were watching, the brightness of the tin cup clouded over, as though with a sudden fog. Anton drew out the thermometer and looked at it.
"The dew-point's only thirty-four," he cried, "and as we've got to figure frost at three or four degrees lower, it'll be so cold that there won't be any fog to stop a freeze. Ross, it's just the night for a killing frost. What do you think we'd better do?"
The older lad hesitated.
"If you don't mind, Anton," he said, "I'll stay to supper, and we'll see what your night observations say."
By evening the threats of a frost were even more definite and the two boys consulted what had best be done.
"I can easily get Father to start his fire-pots," said Ross, "we got them all fixed up this winter. Bob's dad has got some fruit, and we can warn him by wireless, and we could get a lot of the fellows together. I don't want to make a mistake, though. If we suggest that the fire-pots ought to be started and then it doesn't freeze, we'll hurt the League a lot more than we'll help it."
"I wish we could talk it over with Mr. Levin," said Anton, "but he's down with one of his sick spells and we oughtn't to disturb him. Whatever we do, we've got to do it on our own."
"Let's get Bob here," suggested Ross, "he's got a steady head."
"And Fred," Anton added, "he's read all the Weather Bureau stuff on Frosts, I know. He's been writing his articles for theReviewfrom them."
"All right," said Ross, "I'll slip over and call for Fred and you get Bob on the wireless and ask him to come over here."
An hour later, the four boys were poring over the weather maps, comparing notes and observations and trying to decide whether they ought to do anything. Fred, always ready to take up something new, was for plunging ahead, on the chance that there might be frost, but doubted whether a frost was likely. Ross, as head of the League, was a little timid and afraid to make a serious mistake. Anton was firmly convinced that a killing frost would come before morning. Bob settled it.
"Better for the League to be laughed at than chance having the crops ruined," he said.
This turned the scale, and from a discussion of the advisability of frost warning, the question turned to the best way of letting people know. It was decided that Bob should return to his wireless, get as many of his connected operators in touch as possible and get them to warn their districts. Fred, who had persuaded his father to install a 'phone, was to get in touch with the few farmers in the district who had telephones and ask them to spread the warning. Anton was to borrow his father's buggy and drive to points not reached in any other way, and Ross was to go on his pony. By this means, the county would be fairly well covered. The boys were just separating, when Bob stopped.
"Jed Tighe!" he said.
"Oh, let the old skinflint go," said Fred, "there isn't any way of reaching him, any way."
"That doesn't seem quite fair," said Ross, dubiously, "he's got more fruit than anybody else."
"It isn't fair," said Bob.
"I've been wondering," said Anton, "if we oughtn't to notify Jed Tighe somehow."
"We've got to," said Bob.
"And only get rowed at for our pains," declared Fred.
This was so likely that all the boys felt the truth of the remark and there was a moment's silence.
"Play square," said Bob.
"Jed Tighe has never done anything to help the League," said Fred. "I don't see why we should do anything to help him."
"Well," said Ross, "we can't take that stand. Any chap that needs help ought to be warned.If you saw his house on fire, Fred, you wouldn't hesitate to tell Jed Tighe, would you?"
"No," answered the editor doubtfully, "I wouldn't, but this seems different, some way. We might be making fools of ourselves and he'd have the laugh on us for ever."
"Better be laughed at for trying to help than blamed for not trying," repeated Bob.
This was unanswerable and to Ross was deputed the dubious pleasure of notifying the hard old farmer. As the boys separated, Anton looked at his watch.
"It's going to be all hours before you get home to your own place, Ross," said Anton, "it would be a shame if your fruit ran a risk by your being late. Your dad hasn't got a 'phone."
"That's easily fixed," said Ross.
He went to the door and whistled. Rex came bounding up. Ross went to the table and scribbled on a piece of paper:
"Frost to-night! Light the pots!"
This he fastened securely to the Airedale's collar.
"Home! Rex!" he said.
The terrier looked up in his master's face to make sure that it was an order, and not a game,and evidently being satisfied, started down the road at a long sweeping trot. About a hundred yards away he stopped and turned round to look. Ross was expecting this, so raised his arm and pointed. Quite satisfied, Rex swung round to the road again and galloped out of sight.
The boys separated at once, Bob to his wireless outfit, Fred to his 'phone. Anton, however, did not get in the buggy, as arranged. Instead, his father, knowing that the lad was frail, packed him off to bed and drove in the buggy himself, warning all his neighbors. Ross, on his little pony, riding like another Paul Revere, covered many miles. It was well on towards midnight when he reached Jed Tighe's house. The dogs broke out into a furious barking, and, wakened by their tumult, the old farmer with his thin scraggly beard, came to the door.
"What do you want, coming to my house at this hour of the night?" he began, not recognizing his visitor.
"It's me, Ross Planford," the boy answered. "I came to tell you that it's going to freeze tonight."
"That's a nice reason for getting a man out of his bed! Besides, it ain't so. There's neverbeen a frost in this county later'n April 3." He snapped his fingers at the boy. "That's how much you know about it."
Ross found it hard to keep down his temper at this discourtesy.
"It's going to freeze, just the same," he retorted.
"Well, let it freeze, and you, too."
The old farmer began to close the door.
"But your fruit'll all be frosted!"
"Save it yourself, then," snapped Jed Tighe and slammed the door.
Ross dug his heels into his pony and started for home. The ride had taken him six miles out of his way and he was anxious to get home to make sure Rex had delivered his message. Still, as he rode, his pony's hoofs seemed to beat out the message:
"Save it yourself, then!"
Why should he?
Again—
Why shouldn't he?
The gallop came down to a trot and then to a walk, as Ross brooded over what he should do. As it chanced, his path lay near one of the younger members of the League, who had bought a smallwireless outfit, similar to that of Anton's. Ross reined in.
As at Jed Tighe's, the hounds announced his arrival and the farmer poked his head out of the window. He recognized the boy at once.
"What's up, Ross?" he asked. "Anything wrong?"
"There's a killing freeze coming tonight, Mr. Lovell," the boy answered. "We're warning every one with fruit trees to start a smudge going. And, Mr. Lovell, can I use the wireless for a minute?"
"Of course. Much obliged for the tip, my boy, I'll get right up and attend to things. Of course, I don't know as it'll do any good, if it's a goin' to freeze; to my way o' thinkin' it's goin' to freeze and nothin'll stop it. But no one can say that Tim Lovell was too lazy to try an' save his crops."
Ross tied his pony and hurried up to his friend's room. In a minute the wireless was buzzing and presently, back came the answering buzz. Georgie sat up in bed and listened.
"I'll go with you to Jed Tighe's," he said, "that is, if Father'll let me."
"Try it," said Ross, "if he will, you can jump on the pony behind me."
Permission was readily granted, for the farmer was grateful for his own warning, and in less than ten minutes' time the two boys were galloping back along the frosty road to the old skinflint's place.
"Aren't you going to tell him about the frost?" asked George, as Ross turned his pony off on the windward side of the orchard.
"I have told him," answered Ross, and he related the story of the meeting, gathering together dry twigs and branches as he talked.
George waxed indignant.
"I'd let him go to grass!" he said.
"That's what I thought at first," Ross replied, "but if you saw a chap drowning, you'd jump in and save him without waiting to find out whether he was delirious and didn't want to be saved."
"Of course," George answered, "any fellow would jump in."
"That's what we're doing, we're jumping in."
Minutes were precious and the two boys worked with all their might, gathering piles of twigs and dry sticks. There was a heap of straw and stable manure a field or two away, and Ross rolled several wheelbarrow loads of it across the fields. After two hours' work, the boys had a row oflittle piles of fuel, covering one quarter of the length of the orchard.
Fighting frost in an orchard—night.
Fighting frost in an orchard—night.
Fighting frost in an orchard—dawn.
Fighting frost in an orchard—dawn.
The pall of smoke prevents evaporation and keeps the air near the ground from freezing temperatures.
Copyright by J. Cecil Alter, U.S. Weather Bureau, Cheyenne, Wyo.
"You light the first one, Georgie," said Ross, wanting to give the younger lad the honor, for he had worked pluckily and hard.
The lad went down and touched a match to the first pile. It blazed up merrily, and just as the smoke began to rise, the wheels of a buggy were heard along the road. A moment later Bob jumped out.
"Hello!" was all he said.
He cast one glance at the piles and commenced to work with a will. Presently a shout was heard and Ralph, the photographer, appeared on his wheel.
"There's a bunch more coming," he said, and he, too, set to work.
"Frost!" said Bob suddenly, as he pointed to a small glistening crystal of hoar frost on a blade of grass.
The boys cheered. Their prophecies were justified, and they plugged at the work harder than ever. Bob, who feared neither Jed Tighe's tongue, nor anything else, opened the farmer's stable, harnessed and hitched up a team, and commenced to draw the manure and straw to the edgeof the orchard. It was now three o'clock and the frost was beginning to form rapidly.
"We can't save the rest of it," said Ross, as he looked longingly at the far quarter of the orchard; "we've got all we can do to keep going what we've got."
Four o'clock and five o'clock passed. The sun rose. Promptly at five-thirty, his regular hour, old Jed Tighe got up and walked to the window to see what kind of a day it was. He rubbed his eyes and looked again, astonished.
There, on his land, using his team of horses, was a group of eight boys, their forms only occasionally seen through the blanket of smoke which drifted sluggishly over and through the trees of his orchard. The ground was white with hoar frost and the lower branches of the trees in the yard had frost crystals on them. The farmer dressed hurriedly and went out.
A dead silence fell along the boys as the tall spare form of the farmer was seen approaching. Georgie and some of the younger ones shrank back. Ross stood his ground. Bob lounged forward.
Jed Tighe said never a word. He cast a shrewd glance at the fruit trees in the orchard which hadbeen nearest to the fires and the smudges, and then, still silently, walked down the entire line of the fires until the end of it, and beyond. On the unprotected stretch, the frost lay thick. He stood thoughtfully a moment and then walked back up the line, more slowly, until he came to where Ross stood, watching him.
"So you did save it, eh?"
"Yes, Mr. Tighe," the boy said, "I did."
"And I suppose you think I told you to?"
"Yes, you did."
"I'm not any fonder of being made to look like a fool than most men are," the farmer said, "but I'm fair." He turned on his heel and started to walk away. Over his shoulder he snapped:
"Twenty-five per cent of the value of the difference between the fruit on the protected and the unprotected parts of my ground goes to the League. And I'll let my boy, Bill, join you."
The saving of Jed Tighe's crop did more to establish the reputation of the Mississippi League of the Weather than anything which the boys had done since the League was organized. Although Jed Tighe was stern by nature, he was thoroughly fair. He had no hesitation in placing the credit where it belonged, and the boys soon found that they had no stronger ally than the hard-spoken old farmer.
Even his friendship, however, did not prepare the boys for the farmer's sudden arrival at their club-house, on a Saturday afternoon, two weeks later. He drove up in a ramshackle old buggy, driving two of the finest horses in the county. Skinflint though he was, he loved horses. He came into the club-house and eyed the boys standing around the table.
"I'm going to ship some potatoes to Chicago," he said abruptly, without any preface. "I wantto know whether they'll be safe from freezing on the way."
There was a moment's dead silence. The boys had not bargained for such a point-blank demand for help, and it took them off their feet. One looked at the other and several shuffled uncomfortably. The Forecaster watched the lads keenly, interested to see how they would face the issue. Ross spoke first.
"Well, Mr. Tighe," he said hesitatingly, "we haven't done any figuring on the weather outside this neighborhood, as yet."
This cautious attitude did not appeal to Fred, who always wanted to plunge in head first.
"Sure we can, Ross!" he declared.
The president of the League looked inquiringly at his mainstay, the silent Bob, and, in answer to his unspoken question, the other nodded.
"We could try it, of course, if you wanted us to," agreed Ross.
"Ain't I asking you to?" said their visitor, sharply.
"But suppose we don't get it just right?" Ross queried.
"That's the chance I'm taking," the farmer replied. "But there's no doubt that you know a lotmore about it than I do, and your guess is likely to be nearer than mine. Those potatoes have just got to go to Chicago some time next week, anyway."
"It's a new stunt for the League," said Ross again, hesitating, but the editor-in-chief broke in impatiently.
"We might as well tell what we know," he said. "We do know that there's a cold wave on the way."
"There is? How cold?" the farmer asked, with a sudden quickening of interest.
"Cold enough to freeze potatoes, at any rate," assured Fred. "I was looking at the Weather Map only about an hour ago. Oh, it's going to be cold, all right."
"How do you know?" Jed Tighe demanded. "If I'm goin' to act on what you boys say, I'd like to know how you find out."
"I've been wondering," put in Anton thoughtfully, "if it wouldn't be a good idea to have Mr. Tighe go over the map with us. He might be interested in figuring it out, and then if we didn't hit it just right, he'd know we'd done our best, anyway."
Bucking a snow drift.
Bucking a snow drift.
Clear the way!
Clear the way!
Even an avalanche cannot stop Man, backed with the resources of modern snow-fighting machinery.
Courtesy of Northern Pacific Railway Co.
"Well," rejoined the farmer grimly, "if I'vegot to hand you over some of my crop this fall, I might as well find out what sort of project I'm supporting. I really would like to see how you find out. You boys certainly made good on that frost business the other night."
From a hook over the compositor's "case," Fred reached down a sheaf of the Daily Weather Reports, and laid those for the last three days on the table in front of Anton. The Forecaster stood by to help the crippled lad and to correct him if he made any mistakes in his explanations.
"All our weather in the United States," the boy began, explanatorily, "comes from the west."
"Why?" snapped back Jed Tighe.
The Forecaster smiled. He realized that the question went to the very root of weather knowledge. The query was a poser to Anton. He stammered.
"I know it does," he said, "but just why, I—I—"
"You'll have to begin at the beginning, Anton," put in the Forecaster quietly. "If Mr. Tighe really wants to know, you can't take anything for granted. Explain to him the circulation of the atmosphere, just the way I taught it to you during the winter."
The crippled lad's face brightened. He knew, now, how to proceed.
"All changes of weather, Mr. Tighe," he said, "happen because of the winds, and all the changes of winds are due to the differences in heat at various parts of the globe, especially at the equator, where it is always hot, and at the poles, where it is cold nearly all the year round."
"You mean to say that the weather at the North Pole and at the equator has anything to do with our weather here?"
"Everything," Anton answered, nodding his head. "The heat of the sun is what causes weather changes, because winds are due to the heating of the air, and the sun is the only thing that heats the air. At the equator, where the sun shines nearly overhead all the year round, the air gets to be very hot. Hot air expands, and as it gets bigger, it displaces the cold air above it. Gravity pulls down the colder air on both sides of this belt of rising hot air, and the down-flowing cold air on both sides blows in toward the equator under the warm air, where the heat of the sun warms it again, and, in turn, it rises. This is going on all the time and is one of the chief things that starts the winds blowing."
"But winds don't always blow the same way," said the farmer; "you talk as if they did."
"Some of them do," Anton replied. "There are lots of places where the winds hardly change, at all, but always blow in the same direction. You read of sailing ships taking the 'trade winds' when coming from Europe to America. Those are all easterly winds and blow towards the American coasts all the year round."
"I don't see how they can," the other objected.
"They do, Mr. Tighe," the Forecaster interrupted, endorsing Anton's statements; "the trade winds are the downflowing currents of cold air that Anton spoke of, which come down at either side of the equatorial belt to replace the warm air which is rising. The trade winds, however, form only a narrow belt and blow only near the surface of the earth. Above them, you can see the lighter clouds blowing eastward with a westerly wind, so that, quite often, in the trade winds, you can look overhead and see two layers of clouds driving in opposite directions."
"You mean to say that there are different layers of wind?" queried the farmer.
"Sure," put in Ralph, the cloud expert, "I've got photographs that show that up clearly.You've seen clouds going at different rates, haven't you, Mr. Tighe, some fast and some slowly?"
The other nodded and turned to the Forecaster, who continued.
"There are always several layers of wind, and, except above the equatorial belt," he said, "the direction of the upper air winds is generally towards the east."
"How can you tell that?"
"By the clouds, or by kites and balloons. But we don't even need to do this, because there are a few places that rise above the lower layers of the trade winds. Thus, the Peak of Teneriffe, which is in the trade-wind belt, has a continuous easterly wind on its lower slopes and a continuous westerly wind right at the summit.
"This gives three belts of weather in the tropical and sub-tropical zones. The first of these is a light up-flowing east wind on or near the equator—it shifts a little to the north or south with the change of the seasons; a belt of heavy rains and calm, the rains being due to the warm, moist, uprising air cooling by expansion so that the moisture is condensed—this region is known to sailors as the 'doldrums' and many a sailing-vesselhas been held for weeks there, without enough wind to carry her the few miles necessary to get into the next belt of winds; outside this, come the downflowing easterly currents, known as the trade winds, which form a belt between the tropics and the temperate zones. Beyond this—to the north and south of the tropical zones—come the prevailing belts of strong west winds, which stretch almost to the Poles.
"The United States is in this west-wind zone and the strength and regularity of the eastward movement of the weather is because both the winds of the surface and of the upper air blow in the same direction. Naturally, the same conditions are repeated on the other side of the equator. In the southern hemisphere the land masses are not so large and the regularity of the winds is less disturbed. There, the west winds are so strong that certain latitudes are known as the 'roaring forties.' These 'forties' correspond in latitude to the northern third of the United States. Chicago and New York are both in the 'roaring forties' of the northern hemisphere."
"The way you tell it, it sounds all right," the farmer objected, "but from my experience, winds blow from all over the place."
"Locally, perhaps, they seem to," the weather expert responded, "but if you watched them closely, you'd find that about seventy per cent of the winds come from a westerly direction."
"They do here, for a fact," put in Tom, who, as official wind-measurer of the League, had been following the explanation with the keenest attention. "I've noticed that in my kite-flying. The winds are from the southwest or from the northwest nearly all the time."
"You mean both in summer and winter?"
"Yes," answered Tom, "they're more from the northwest in winter, I think, but they're generally westerly."
"If the winds are due to the position of the equator and the poles," the old farmer said shrewdly, "I don't see why summer and winter ought to make any difference."
"That," said the Forecaster, "is due to an entirely different set of conditions. It's due to the difference in radiation. There's much greater change in temperature over the land than over the sea. Take an island like Bermuda, for example. From the hottest day in summer to the coldest day in winter there isn't a change of more than forty degrees, because Bermuda is surrounded by waterand is near warm ocean currents. In Arizona, on the other hand, there's a change of as much as fifty degrees of temperature in a single day. That is because land absorbs heat quickly and lets it go equally quickly. The interior of a continent in summer time heats and expands the air in the same way that the air is heated over the equator, and, in the same manner, sets in motion another system of winds, for cold air comes rushing down from all sides and forces up the rising warm air.
"Take Asia, for example, where the continental mass is large and the plateaus high. The interior becomes so hot that the air is sent up like the draught in a big chimney, and cool winds from the sea blow toward the interior from all sides in the summer time, and away from it, to all sides, in the winter time. That's what causes the famous Indian monsoons, which blow steadily to the north-east for the six months of summer and just as steadily to the south-west for the six months of winter. The native boats, there, are built on purpose for the monsoon, so that they can only sail with a fair wind and they make one round trip a year, going south with the monsoon in winter and returning with the summer monsoon."
The old farmer scratched his head.
"There's more to this than I thought," he said; "I always supposed that winds just happened."
"No, indeed," the Forecaster answered, "every place in the world has its own system of winds, though in some parts there are so many variations that it isn't always easy to distinguish between the regular and the irregular currents. In the United States the surface winds are very irregular, for we live in one of the stormiest regions of the entire world. Still, that doesn't alter the general rule that all our weather comes from the west."
"And yet," said the farmer, in a puzzled manner, "I don't see why it comes from the west."
"I think I can explain it to you," the weather expert replied. "You know that when water is running down a hole at the bottom of a basin, if it is in motion it doesn't go down straight but with a circular movement, finally making a whirlpool?"
"Of course," the farmer said.
"So does air," the Forecaster rejoined. "There is something the same sort of a whirl at the poles. The prevailing westerly winds of the United States are due to this circumpolar whirl, though modified and altered by the changes of theseasons, the differences of heat between day and night, the radiation from the land, the irregularity of the coastline, the currents of the ocean and a thousand other factors. Each of these the Weather Man has to study when he makes a forecast, but, in the United States, his work is aided by the fact that weather always travels eastward and that the storm follows regular tracks, sharply outlined, like Indian trails across the country."
"Roads in the air?" queried Fred.
"Yes, my boy," the Forecaster answered, "regular roads in the air. There used to be an old saying: 'American weather is made at Medicine Hat.' In a sense this was true, for about sixty per cent of the storm areas—'lows' or region of low barometric pressure—come from the Canadian Northwest. The St. Lawrence Valley is the outlet for our storms. You know the saying about the St. Lawrence, don't you?"
"No, tell us, Mr. Levin," begged Fred, always eager for some weather saying which he could put into theReview.
"Up there," the Forecaster rejoined, "they say that when a stranger complains about the weather, a native will reply, 'Don't mind this, we'll have another sample along in about five minutes.'And, sure enough, they do. The St. Lawrence Valley is a magnet for weather changes and has, perhaps, more storms than any other valley in the world."
"You spoke of the 'roads in the air,' sir," put in Ross, "how many are there?"
"Five regular trails," the Forecaster answered. "The northernmost one begins at the Canadian Northwest, runs along the International Boundary, crosses the Lake region and disappears up the St. Lawrence Valley. The second starts at the same point in the Canadian Northwest, travels southeast to the lower Mississippi Valley—a little north of where we are now, boys—curves up to the Ohio Valley and also escapes by the St. Lawrence route.
"A third storm track strikes into the Pacific Coast a little north of San Francisco and runs east and a little south until it joins the Ohio Valley and St. Lawrence track. A fourth develops in the southwestern states and runs along Texas and the gulf states to the Florida coast, where it curves northward along the Atlantic coast, though a few storms take a sharp turn in the Mississippi Valley and go Ohiowards. The fifth storm track is that of the West Indian hurricanes,which whirl around the West Indies and enter the United States south of Cape Hatteras or from the Gulf of Mexico and pass north or northeastward. A few of these hurricanes—like the famous Galveston type—sweep westwards a long way before the northward movement sets in. This type also goes to the St. Lawrence Valley.
"These five tracks are clearly marked, but as such areas are a thousand miles across, it follows that the country for five hundred miles on either side of the lines has its weather governed by them. Knowing these tracks is of great importance in forecasting weather, because, while you cannot always tell exactly what a storm is going to do, you definitely know some of the things that it will never do."
"What sort of things, sir?" asked Fred.
"Well, my boy," the Forecaster answered, "if there's an area of low pressure in Dakota, we know that it won't strike California; if there's one in New York, we know that Maryland is safe. A storm will never go down the Mississippi, nor up the St. Lawrence, but will always travel up the Mississippi and down the St. Lawrence."
"There does seem to be something regular about it," the farmer remarked, his interest growing, as the Forecaster took his pencil and sketched out, across the map of the United States, the five great storm tracks. "That's all right for storms, maybe. But how about a cold wave? Fred, here, said that a cold wave was coming. Can you figure that out in the same way?"