CAPTAIN HENRY KATER, F.R.S., &c.
Born April 16, 1777. Died April 26, 1835.
Captain Henry Kater, distinguished by his mathematical and physical researches during the space of nearly half a century, was born at Bristol; his father was of a German family, and his mother was the daughter of an eminent architect; both were distinguished for their scientific attainments, and united in imbuing their son with a similar taste. Henry was, however, destined by his father for the law, and had with great reluctance to give up for a time hishitherto exclusive devotion to abstract science. Mr. Kater continued for two years to remain in a pleader's office, during which time he acquired a considerable portion of legal knowledge, on which he valued himself through life; but the death of his father, in 1794, permitted him to resume his favourite studies; and bidding adieu to the law, he obtained a commission in the 12th Regiment of Foot, at that time stationed in India.
During the following year, Mr. Kater was engaged in the trigonometrical survey of India under Colonel Lambton, contributing greatly, by his untiring labours, to the success of that vast undertaking. About the same period, he was also occupied in constructing a peculiarly sensible hygrometer, of which he published a description in the 'Asiatic Researches.' Mr. Kater remained in India seven years, during which time his unremitting study in a hot climate greatly injured his constitution, and was the cause of his falling into a state of ill health, from which he suffered more or less until the end of his life.
On his return to England, he qualified himself to serve on the general staff, and later in life retired on half-pay, from which period he devoted himself entirely to science. When Parliament, in the years 1818-19, determined on establishing an uniform system of weights and measures, Captain Kater, in conjunction with Sir Joseph Banks, Sir George Clerk, Davies Gilbert, and Drs. Wollaston and Young, was appointed to investigate this most important subject; and he instituted a series of experiments with a pendulum made of a bar of brass, 1½ inches wide and ⅛ of an inch thick, to which two knife-edges of a kind of steel prepared in India, and known by the name of wootz, were attached, playing upon agate plates. The knife-edges were placed in a parallel direction on the brass bar, facing opposite ways upon either of which it might be swung. They were so arranged, that when either was used as the point of suspension the other nearly represented the centre of oscillation, and by means of a small adjustable weight, this condition might be accurately fulfilled. These experiments were made in the house of Mr. H. Browne, F.R.S., which was situated in a part of Portland Place not likely to be disturbed by carriages. They occupied Captain Kater's close attention for several years; and he has permanently attached his name to the beautiful theorem of Huygens respecting the reciprocity of the centres of oscillation and suspension, and their consequent quality of convertibility. Although this was a property already known to belong to the centre of oscillation, it had never hitherto been practically applied to determine the exact length of a pendulum vibrating seconds; it was, therefore, highly creditable to his ingenuity, and claims the same order of merit as an original invention. In this, as well as in Kater's laborious inquiries respecting a standard of weights and measures, even where his conclusions have not escaped all the chances oferror, he has led the way to the still more delicate researches which have followed.
Captain Kater also instituted a series of experiments as to the best kind of steel and shape for compass needles; it resulted in the adoption of the shear clock-spring steel, and the pierced rhombus form, in the proportion of five inches in length to two in width. In the year 1831 he received the gold medal of the Royal Astronomical Society, for the construction of his floating collimator, an instrument for ascertaining the accurate zero or level points of divided astronomical instruments. The optical principle upon which it depends is a very beautiful one, and the invention of Kater, with several improvements in point of form, has become the auxiliary of nearly every observatory in the world, being one of those small but happy improvements which affect materially the progress of science. Most of the learned societies in Great Britain and on the Continent testified at different times their sense of the value of his services, by enrolling him among their members. The Emperor of Russia employed him to construct standards for the weights and measures of his dominions, and was so pleased with the execution of them, that he presented Kater with the Order of St. Anne and a diamond snuff-box. The greater part of his publications appeared in the 'Philosophical Transactions' of the Royal Society, chiefly between the years 1813 and 1828.
Captain Kater died from a severe affection of the lungs, at his residence, York Gate, in the fifty-third year of his age.—Athenæum, May, 1835.—Weld's History of the Royal Society.London, 1848.—Monthly Notices of the Royal Astronomical Society, vol. 3, February, 1836.—Sixth Dissertation Encyclopædia Britannica, Eighth Edition.