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. SIR JOHN LESLIE, F.R.S.E., &c. Born April 16, 1766. Died November 3, 1832. Sir John Leslie, Professor of Natural Philosophy in the University of Edinburgh, the son of a poor joiner or cabinetmaker, was born at the village of Largo, in the county of Fife. Although both weak and sickly as a child, he soon acquired considerable knowledge of mathematical and physical science, and at the age of eleven attracted the notice of Mr. Oliphant, the minister of the parish, by his precocious attainments. This gentleman kindly lent young Leslie some scientific books, and strongly advised him to continue the study of Latin, for which he had a great aversion, although in after life he attained considerable proficiency in that language.