Part 10

On the completion of these docks his professional services were engaged by the citizens of Bristol, to effect a great and comprehensive measure of harbour improvement, designed to place the port of Bristol at once in the foremost position with respect to commercial advantages. This was the conversion of part of the river Avon into an immense floating dock, capable of accommodating 1400 vessels. Mr. Jessop was also at this time occupied in constructing the Surrey iron railways, which consisted of a double tramroad, from the Thames at Wandsworth to the town of Croydon, with an extension from Croydon to Godstone and Merstham; they are principally remarkable as being the first public railroads constructed in the south of England. The whole of these tramroads were afterwards bought and taken up by the Brighton Railway Company. Mr. Jessop was likewise connected with the Caledonian Canal, which he was specially called upon to survey before its commencement, and of which he continued to be the consulting engineer for many years.

In concluding this brief notice of Mr. Jessop's life, it remains only to be said that with him exclusively originated the idea of taking advantage of the immense floods to which certain districts are subject, by storing these waters up for the gradual and regular supply of his canals. In addition to this he shares with Mr. Telford the honour of first using iron in the construction of the troughs of aqueducts, and for the heads, heel-posts and ribs of lock-gates, as adopted on the Caledonian and Ellesmere canals.--_Memoir of William Jessop, by Samuel Hughes, C.E._

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 his hitherto 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 1/8 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 of error, 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.

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.

He also became known to Professors Robison and Stewart, of Edinburgh, and by their advice was sent, in his thirteenth year, to the University of St. Andrew's, to study mathematics under Professor Vilant. Here, at the end of the first session, his abilities procured him the second prize, and likewise attracted the notice of the Earl of Kinnoull, then Chancellor of the University, who undertook to defray the expenses of his education, provided that he would enter the Church. Leslie prosecuted his studies at this university during six sessions, and became about this time acquainted with Playfair and Dr. Small.

In 1783-4 he quitted St. Andrews and went to Edinburgh, where, though he formally entered the Divinity Hall, he contrived to devote his first session to the sciences, particularly chemistry; in fact, Leslie seems early to have relinquished all thoughts of the Church--a resolution hastened by the death of his patron, the Earl of Kinnoull, shortly after his removal to Edinburgh. While engaged at the university, he also acted as tutor to Mr. Douglas, afterwards Lord Reston, the nephew of Dr. Adam Smith, and he thus became known to that philosopher, who treated him kindly, and occasionally favoured him with directions as to his pursuits. Leslie's first essay, 'On the Resolution of Indeterminate Problems,' was composed about this time, and read to the Royal Society of Edinburgh by Mr. Playfair, in 1788, and published in their 'Transactions' for 1790.

In 1788, he became tutor to two young Americans of the name of Randolph, and accompanied them to Virginia, where he remained for about a twelvemonth, during which time he visited New York, Philadelphia, &c. In January 1790, carrying, among other letters of recommendation, one from Adam Smith, Leslie repaired to London, with the intention of delivering a course of lectures on natural philosophy; but finding, to use his own words, that "rational lectures would not succeed," he employed himself for some time in writing for the 'Monthly Review,' and in other literary occupations.

In April 1790, he became tutor to the younger Wedgewoods, of Etruria, in Staffordshire, who had been his former fellow-students, and with whom he remained until the close of 1792. Leslie was likewise employed during this period in experimental investigations, and in completing a translation of Buffon's 'Natural History of Birds,' published in 1793, in nine volumes, for which he received a considerable sum,--the foundation of that pecuniary competency which his industrious and prudent habits enabled him ultimately to acquire.

During the years 1794-5 he resided at Largo, occupied upon a long series of hygrometrical experiments, during the course of which he invented his differential thermometer, the parent, as it may be called, of his subsequent inventions--the hygroscope, photometer, pyroscope, æthrioscope, and atmometer. Although Leslie has been accused of having plagiarized this invention either from Van Helmont, who died in 1644, or from John Christopher Sturmius, who died sixty years later, he at all events showed, by his skilful and fruitful employment of the disputed invention, how much he surpassed, and how little he needed the help of, him whom he is ungenerously supposed to have robbed of his legitimate honours.

In 1800 he wrote several papers, on different branches of physics, in Nicholson's 'Philosophical Journal,' which resulted in the publication at London, in 1804, of his 'Experimental Inquiry into the Nature and Propagation of Heat.' The originality and boldness of the peculiar doctrines contained in this work, and the number of new and important facts disclosed by its ingenious experimental combinations, rendered it an object of extraordinary interest in the scientific world. The Royal Society of London unanimously adjudged to its author the Rumford medal; and although paradoxical in many of its theories, defective in arrangement, and over ambitious in style, this work is almost unrivalled in the entire range of physical science, for its indication of vigorous and inventive genius.

Previous to this period of life, Leslie had appeared twice as a candidate for an academical chair; first in the University of St. Andrew's, afterwards in that of Glasgow; but on both occasions without success. He now became a candidate for the Mathematical chair at Edinburgh, vacant through the promotion of Professor Playfair to the chair of Natural Philosophy. After a severe contest, during which much party spirit was displayed, owing to his principal competitor, Dr. Thomas Macknight, one of the ministers of Edinburgh, being supported by the majority of the city clergy, Leslie was, in March, 1805, elected to the Mathematical chair. He entered immediately upon his official duties, which he continued to discharge with zeal and assiduity during the following fourteen years.

Notwithstanding the labours which these duties entailed upon him, Leslie continued his experimental inquiries, and in June, 1810, discovered his beautiful process of artificial congelation, by which he was enabled to produce ice, and even to freeze mercury at pleasure. The process consists of a combination of the powers of rarefaction and absorption, effected by placing a very strong absorbent under the receiver of an air-pump. This experiment was performed in London in 1811, before a meeting of some members of the Royal Society; and the discovery was announced in the same year in the 'Memoirs' of the French Institute. He explained his experiments and views on this subject in 1813, in a volume published at Edinburgh, entitled, 'A short Account of Experiments and Instruments depending on the Relations of Air to Heat and Moisture.' Closely connected with the subject of this treatise was an ingenious paper, published in 1818, in the 'Transactions' of the Royal Society of Edinburgh, under the title, 'On certain Impressions of Cold transmitted from the Higher Atmosphere; with a Description of an Instrument to Measure them.' The æthrioscope was the instrument here alluded to.

In 1819, upon the death of Playfair, Leslie was called to the chair of Natural Philosophy, when his first care was directed to the extension of the apparatus required in the more enlarged series of experiments which he thought necessary for the illustration of the course. "This, indeed," says his biographer, Mr. Napier, "was an object of which he never lost sight; and it is due to him to state, that, through his exertions, the means of experimental illustration in the Natural Philosophy class were for the first time made worthy of the place."

In 1823 he published, chiefly for the use of this class, his 'Elements of Natural Philosophy,' a second edition of which was published in 1829, with corrections and additions. Besides the above-mentioned works, Leslie wrote the following:--'Elements of Geometry, Geometrical Analysis and Plane Trigonometry,' in 1809; 'Observations on Electrical Theories,' published in 1824, in the 'Edinburgh Philosophical Journal;' also many articles in the 'Edinburgh Review;' and the articles on Achromatic Glasses; Acoustics; Aeronautics; Andes; Angle and Trisection of Angle; Arithmetic; Atmometer; Barometer; Barometrical Measurements; Climate; Cold and Congelation; Dew; Interpolation; and Meteorology, in the seventh edition of the 'Encyclopædia Britannica.'

Early in the year 1832, on the recommendation of Lord Brougham, then Lord High Chancellor, Leslie was created, along with several other eminent men of science, a Knight of the Guelphic Order. He was also a member of the Royal Society of Edinburgh, and in 1820 had been elected a corresponding member of the French Institute. During the month of October, whilst engaged in superintending some improvements on his grounds, he caught a severe cold, which was followed by erysipelas in one of his legs, and his neglect of this, owing to a contempt for medicine, and great confidence in his own strength and durability, resulted in his death, at Coates, in the November following, at the age of sixty-six.

Sir John Leslie has been described as rivalling all his contemporaries in that creative faculty which discovers, often by an intuitive glimpse, the hidden secrets of nature; but possessing in a less degree the powers of judgment and reason, being thus often led in his speculations to results glaringly inconsistent. His exquisite instruments, and his experimental combinations, will, however, ever test the utility, no less than the originality of his labours, and will continue to act as aids to farther discovery.--_Encyclopædia Britannica_, Eighth Edition.--_Abstract of Memoir of Sir John Leslie, by Macvey Napier, English Cyclopædia._ London, 1856.

NEVIL MASKELYNE, D.D., F.R.S.

MEMBER OF THE INSTITUTE OF FRANCE, ETC.

Born October 6, 1732. Died February 9, 1811.

This most accurate and industrious astronomer was born in London, and was the son of Mr. Edmund Maskelyne, a gentleman of respectable family in Wiltshire. At the age of nine Maskelyne was sent to Westminster school, where he early began to distinguish himself, and to display a decided taste for the study of optics and astronomy.

The great solar eclipse, which occurred in 1748 was, however, the immediate cause of his directing his attention to these sciences, and from that period he devoted himself with ardour to the study of mathematics as subservient to that of astronomy. It is a curious fact that the same eclipse is said to have produced a similar effect upon the French astronomer Lalande, who was only three months older than his English contemporary.

Soon after this Maskelyne entered the University of Cambridge as a member of Catherine Hall, removing afterwards to Trinity, where he took the degree of Bachelor of Arts with great credit in 1754, and proceeded regularly through the succeeding stages of academical rank in divinity. In 1755 he was ordained to a curacy at Barnet, and in the following year obtained a fellowship at Trinity. In the year 1758 he was elected a fellow of the Royal Society, previous to which event he had become acquainted with Dr. Bradley, and had determined to make astronomy the principal pursuit of his life, feeling that it was perfectly compatible with an enlightened devotion to the duties of his own profession.

1761 marks the period when Maskelyne commenced his public career as an astronomer. During that year he was chosen by the Royal Society to undertake a voyage to the island of St. Helena, for the purpose of observing the transit of Venus; and in order to make the voyage as useful as possible, Maskelyne undertook to make observations upon the parallax of Sirius. He remained ten months at St. Helena, but the weather hindered his observing the transit to advantage, while the inaccuracy of his quadrant, which was of the same construction as was then usually employed, prevented his observations on the stars from being as conclusive as he had expected. His voyage was, however, of great service to navigation, by promoting the introduction of lunar observations for ascertaining the longitude; and he taught the officers of the ship in which he was in, the proper use of the instruments as well as the mode of making the computations.

On his return to England, Maskelyne published, in 1763, his 'British Mariner's Guide,' the earliest of his separate publications, in which he proposes the adoption of a Nautical Almanac according to the plan indicated by Lacaille, after his voyage to the Cape of Good Hope. In the same year he performed a second voyage to the island of Barbadoes, in order to determine the rates of Harrison's chronometers. In his report on the results of this voyage Maskelyne, while doing justice to the works of this eminent mechanician, decided in favour of the employment of lunar observations for determining the longitude, strongly supporting the cause of Professor Mayer, who had computed lunar tables for this purpose. The liberality of the British Government, however, bestowed on Harrison the whole reward that he claimed,[22] while Maskelyne, having been appointed to the situation of Astronomer Royal which likewise made him a member of the Board of Longitude, was instrumental in procuring a reward of 5,000_l._ for the family of Professor Mayer, and a compliment of 300_l._ for Euler, whose theorems had been employed in the investigation.

When the merits of Mayer's tables had been fully established, the Board of Longitude was induced to promote their application to practical purposes by the annual publication of the Nautical Almanac, which, during the remainder of his life, was arranged and conducted entirely under Maskelyne's direction.

Maskelyne held the situation of Astronomer Royal for forty-seven years, during which period he acquired the respect of all Europe, by the diligence and accuracy of his observations, which he always, if possible, conducted in person, requiring the aid of only one assistant.

Up to Maskelyne's time the observations of the Astronomers Royal had been considered as private property; Flamsted publishing his own, while Bradley's were very liberally bought of his family, and afterwards printed by the University of Oxford. Dr. Maskelyne, on the contrary, obtained leave from the British Government to have his observations printed at the public expense under the direction of the Royal Society, who are the legal visitors of the observatory, appointed by the royal sign manual; and by thus causing the observations of the Astronomer Royal to be recorded publicly, he supplied a great want which had hitherto existed both in the English and French establishments. He also made several improvements in the arrangement and employment of the instruments used in the observatory, particularly, by enlarging the slits through which the light was admitted; by making the eyeglass of his transit telescope moveable to the place of each of the wires of the micrometer; and above all, by marking the time to tenths of a second, a refinement which had never been attempted before.

Maskelyne received his doctor's degree in the year 1777, he also obtained the rare distinction of being made one of the eight foreign associates of the French Academy of Science. In consequence of an unsuccessful attempt made by Bouguer to measure the local attraction of a mountain in South America, Maskelyne determined, in 1772, to ascertain that of Schehallien in Scotland; and this latter undertaking, together with the determination of the lunar orbit from observation, and its application to navigation, may be considered as his most important contributions to the cause of science.

In character Dr. Maskelyne was modest and somewhat timid in receiving the visits of strangers, but his ordinary conversation was cheerful and often playful, with a fondness for point and classical allusion. He inherited a good paternal property, and obtained considerable preferment from his college; somewhat late in life he married the sister and co-heiress of Lady Booth of Northamptonshire; his sister was the wife of Robert Lord Clive, and the mother of the Earl of Powis. Dr. Maskelyne died on the ninth of February, 1811, in his seventy-ninth year, leaving a widow and an only daughter.--_Notice sur la vie et les travaux de M. Maskelyne par Delambre._ London, 1813.--_Memoir by Dr. T. Young, Encyclopædia Britannica._

HENRY MAUDSLAY.

Born Aug. 22, 1771. Died Feb. 14, 1831.

This distinguished mechanical engineer was descended from an eminent Lancashire family, who trace back their origin as far as the year 1200. His father in early life enlisted in the Royal Artillery at Norwich, and afterwards became store-keeper at the Royal Dockyard of Woolwich, where his son Henry was born and spent his boyhood, acquiring in the dockyard the first rudiments of that mechanical knowledge which has since made him so justly celebrated.