iron into great permanent structures exposed to heavy strains.* This bridge was commenced in 1819, and opened for traffic in 1826. The distance between the two piers is 550 feet, and the whole roadway, which is carried over four arches on the one side, and three on the other, has a length of 1000 feet, and a breadth of 30 feet. The total cost of the work was 120,000%.

Mr. Telford also built many other bridges of considerable size, and executed some important harbour works at Aberdeen and Dundee; but his most striking performance of this latter class is the St. Katharine Docks, London. One of his latest engagements was the survey of Dover harbour, undertaken in January, 1834, at the request of the Duke of Wellington, (as Warden of the Cinque Ports,) with a view to the adoption of measures to check the accumulation of shingle at the entrance.

During the course of his life Mr. Telford taught himself Latin, French, and German, so as to be able to read those languages with fluency, and to be able to converse freely in French. He is likewise said to have been well acquainted with algebra, but to have placed more reliance upon experiment, than on mathematical investigation. He contributed to the 'Edinburgh Encyclopædia' the articles'Architecture,' 'Bridge Building,' and 'Canal Making.' Besides the above, he wrote an account of his own life, giving elaborate descriptions of his various professional undertakings. (Life of Thomas Telford, written by himself. Edited by John Rickman. London, 1833, 4to.)

Although Telford was not connected with the Institution of Civil Engineers at its formation, he accepted their invitation in 1820, and became their President; and from that time he was unremitting in his attention to the duties of the office, having become by his partial retirement from business, a pretty regular resident in the metropolis.

Telford was possessed of a robust frame, and till he had reached the age of seventy, had never been visited with any serious illness. While at Cambridge, in the year 1827, he was afflicted with a severe and dangerous disorder; and although he gradually recovered a certain degree of health, he never regained his former vigour. He died a few years afterwards at his house in Abingdon Street, Westminster, having completed the seventy-seventh year of his age. His remains were deposited in Westminster Abbey, where there is a statue erected to his memory.-Encyclopædia Britannica.-English Cyclopædia.

Sixth Dissertation, by Dr. J. D. Forbes, F.R.S.-Encyclopædia Britannica. Eighth Edition.

G

CHARLES TENNANT.

Born May 3, 1768. Died October 1, 1838.

Charles Tennant, the founder of the celebrated chemical works at St. Rollox, Glasgow, was born at Ochiltree, Ayrshire. His father, John Tennant, was factor or steward to the Countess of Glencairn, and also rented a farm on her estate, in the culture of which he displayed great practical and scientific ability. John Tennant married twice; after the death of his first wife, by whom he had two sons and one daughter, he married, in the year 1757, Margaret McLure, who, in the course of time, brought him a numerous family of six sons and seven daughters. John Tennant's second wife possessed very superior abilities, which she earnestly directed to the education and advancement of her family, ultimately having the satisfaction of seeing all her children turn out men of energy and success in life. Charles Tennant, the subject of our memoir, was the fifth son; he received his early education at home, afterwards attending the parish school of Ochiltree. When still very young, Charles left home and went to Kilbarhan, with the intention of learning the manufacture of silk. After remaining at this place a short time, Tennant removed to Wellmeadow bleachfield, where he studied the methods of bleaching at that time in use, and ultimately went to Darnly (the place from which the unfortunate husband of Mary, Queen of Scots, took his title), and established there an extensive bleachfield, taking into partnership with him Mr. Cochrane of Paisley. Mr. Tennant now devoted himself to the study of chemistry, feeling that the process of bleaching could only be effected by true chemical agency, whatever might be the particular method or operation, and that, therefore, the bleacher must in the first case look to the chemist for the discovery of more potent agents to effect his object. Before Mr. Tennant's time the operation of bleaching was of a very tedious and expensive nature. The cloth was steeped in alkaline lye, which was called 'bucking.' The subsequent process of bleaching was done by exposure on the grass, called 'crofting;' these operations were repeated five or six times, and extended over a period of eight or ten weeks. In the year 1787 an important change took place, in consequence of the discovery, by Mr. Scheele, of Sweden, of chlorine, which was used as a substitute for exposure to the atmosphere. The repeated experiments of Berthollet added considerably to the facts already known, while the practical effects of these discoveries were still more fully shown by Mr. Watt, and Dr. Henry of Manchester. In 1798 Mr. Tennant made his first great discovery, viz., a method of making saturated chloride of lime, an article which was found to answer perfectly all the purposes required by the bleacher. This invention,

for which he took out a patent, consisted in the substitution of lime for potash. His patent right was, however, resisted by certain of the bleachers of Lancashire, and was set aside by the verdict of a jury, on the grounds that the patent included a mode of 'bucking' with quicklime and water, which was not a new invention; and because one part of the patent was not new, the whole of the claim must be set aside. By this decision the use of liquid chloride of lime in bleaching was thrown open to all; and through an unfortunate error of expression in describing his process, Mr. Tennant was deprived of the fruits of a laborious investigation extending over a period of several years. This subsequently caused a strong feeling of sympathy to be manifested for him by many of the bleachers of Lancashire, who, as an expression of their grateful acknowledgment, presented him with a service of plate, which he accepted. Mr. Tennant, however, in accordance with the character of his original design, determined to press onward with his discoveries, and to bring, if possible, his first invention to a still more practical issue. He therefore adopted a new method, and at length completed and secured by patent a process for impregnating quicklime in a dry state with chlorine, which proved perfectly successful; this, his second patent, remained uncontested, and he lived to secure a large pecuniary reward.

Mr. Tennant's discoveries, together with the introduction of sodaash or 'British soda,' in place of potash, greatly facilitated and cheapened the process of bleaching, while the introduction of mechanical appliances and the power of the steam-engine superseded the previous laborious operations by hand. The result has been that the same amount of bleaching is now performed in as many days as was formerly performed in weeks, while the price has been reduced from 7s. 6d. (1803) to 6d. (1861) for a piece of cloth of 28 yards.

In the year 1800 Mr. Tennant removed from Darnly to St. Rollox, Glasgow, where he commenced business as a large manufacturing chemist, taking into partnership Mr. Charles Mackintosh, Mr. William Cowper, and Mr. James Knox. During the remainder of his life Mr. Tennant devoted himself with energy to the forwarding of his business, and ultimately caused his manufactory to become the largest and most extensive of its kind in Europe. He also took considerable interest in the politics of the day. His principles were those of an intelligent and liberal-minded reformer, and he was long looked up to as one of the leading men of his party, although the least tainted by mere party spirit or selfishness. Mr. Tennant was likewise conspicuous in his promotion of many public undertakings. He took a deep interest in the furtherance of the railway system; the Garnkirk and Glasgow Railway may be said to owe its origin and completion almost entirely to him, while his invincible industry and perseverance contributed greatly towards the establishment of

the Edinburgh and Glasgow Railway. He was a great friend of George Stephenson's, and was present with him at the opening of the Liverpool and Manchester Railroad when the unfortunate accident occurred which resulted in the melancholy death of Mr. Huskisson.

Mr. Tennant died rather suddenly, in his seventy-first year, at his house in Abercrombie Place, Glasgow. He was possessed of a constitutional nervousness, rather remarkable in one of a large and healthy frame, allied to a peculiar sensitiveness to the beautiful. In after life he would often talk with pleasure of his youthful reminiscences of the poet Burns, who was at that time on terms of considerable intimacy with his family. Mr. Tennant was an earnest and indefatigable promoter of economical and educational improvement; an uncompromising friend of civil and religious liberty; while his own inborn energy of character and clear intellect placed him among the foremost of those men who, by uniting science to manufactures, have at once extended their fields of action, and entitled their occupations to be classed among the ranks of the liberal professions.-The Progress of Science and Art as developed in the Bleaching of Cotton, by Henry Ashworth, Paper read before the British Association at Manchester, September 5, 1861; and, Particulars communicated by the Family.

THOMAS THOMSON, M.D., F.R.S.

Born April 12, 1773. Died July 2, 1852.

Dr. Thomas Thomson, Regius Professor of Chemistry in the University of Glasgow, who exercised a remarkable influence in the development and extension of the science of chemistry during the present age, was born at Crieff, in Perthshire. He received his early education at the parish school of that place, and after remaining for a time under the care of Dr. Doig, of Stirling, went to the University of St. Andrews, where he remained for a period of three years. Thomson entered upon his medical studies at the University of Edinburgh, and during the session of 1795-96 attended the lectures of the celebrated Dr. Black, who first awoke in him the latent taste for that science of which he was destined to become so bright an ornament. In 1796 he became connected with the Encyclopædia Britannica, for an early edition of which he wrote the articles— Chemistry, Mineralogy, Vegetable Substances, Animal Substances, and Dyeing Substances, &c. These articles formed the basis of his

system of chemistry, which he published at Edinburgh in the year 1804, in four volumes, and afterwards greatly enlarged and improved as the demand for the book increased. Dr. Thomson commenced delivering a series of lectures on chemistry at Edinburgh in 1800, which were continued with increasing popularity until 1810. Meanwhile he invented the system of chemical symbols now generally adopted by all men of science (with variations as the time demands), and without which chemical language would be unintelligible. He was also the first to open a laboratory in Great Britain for practical manipulation in chemistry. In 1810 he published his 'Elements of Chemistry,' and in 1812 visited Sweden, and on his return wrote a description of that country. The following year to this Dr. Thomson started in London the Annals of Philosophy,' a scientific journal, which he continued to edit until the year 1822, and which a few years afterwards was merged in the 'Philosophical Magazine.' He also about this time conducted for the Board of Excise a series of investigations on brewing, which formed the basis of Scottish legislation on that subject.

In the year 1817 Thomson was elected lecturer on chemistry in the University of Glasgow, and in the following year received the title of Professor. This chair he held until his death, being assisted in his latter years by his nephew and son-in-law, Dr. R. D. Thomson. When Dalton had worked out his grand discovery of the Atomic Theory, he communicated the result of his researches to Thomson, who at once perceived the value and importance of the discovery, and in the year 1807 was the first to publish it to the world. He gave a sketch of this grand theory in the third edition of his System of Chemistry;' and we are chiefly indebted to the labours of Professor Thomson, conjointly with Dr. Henry of Manchester, and Dr. Wollaston, for luminous views on this important subject. In 1825 Dr. Thomson wrote, in two volumes, 'An Attempt to Establish the First Principles of Chemistry by Experiment.' In 1830-31 he published his 'History of Chemistry, a work which has been described as a masterpiece of learning and research. In 1836 appeared his 'Outlines of Mineralogy and Geology;' and in 1849 he issued his last work, 'On Brewing and Distillation.'

Thomson performed in science, and its history and literature, a very great amount of valuable labour, and acquired a distinguished reputation both as an original discoverer, and as a practical teacher of his favourite science. He died in 1852, at the age of seventynine, and has left behind him a son who bears his name, now (1860) superintendent of the East India Company's Botanic Gardens at Calcutta, and one of the most distinguished scientific botanists of the day. Encyclopædia Britannica, Eighth Edition.-English Cyclopædia. London, 1858.