travel in France, whither he proceeded, accompanied by his lady and Mr. Faraday. From France, Davy proceeded to Italy, where he spent the winter, returning to London on the 23rd of April, 1814. During his stay in Italy, he collected specimens of the colours used by the ancients in their pictures. This formed the subject of a memoir to the Royal Society, the most interesting part of the paper being the announcement that the fine blues of the ancients were formed of silex, soda, and copper, and that they may be exactly imitated by strongly heating together, for the space of two hours, three parts of copper filings, fifteen of carbonate of soda, and twenty of powdered flint.

In the year 1816, Davy turned his attention to a method of preventing the dreadful accidents in coal mines, from explosions of the fire-damp. After considerable investigation, he found that this gas would not explode when mixed with less than six times or more than fourteen times its volume of atmospheric air; and in the course of experiments made for the purpose of ascertaining how the inflammation takes place, he was surprised to observe that flames will not pass through tubes of a certain length or smallness of bore. He then found that if the length was diminished, and the bore also reduced, that flames still would not pass; and further, that the length of the tubes might safely be diminished to hardly anything, provided their bore was proportionably lessened. Working from these principles, he proposed several kinds of lamps, but all were finally superseded by the simple one known as the Davy safetylamp, in which a small oil light is covered by a cylinder of wire gauze, the small apertures* of which flame will not pass through, and the explosion is thus prevented from extending outside the wire gauze. The introduction of this beautiful invention, although freely given to the public, was for a time violently opposed by prejudice and passion. Experience, however, showed the comparative safety which the miners who used it possessed, and the coal-owners of Newcastle and the vicinity presented Davy with a superb service of plate, as some recognition of the important benefit he had conferred on them.

During the later years of Sir Humphry Davy's life, various communications appeared from him to the Royal Society, none, however, presenting any very remarkable features. In November, 1820, a few months after the death of Sir Joseph Banks, he was elected president of the above society. In 1823 he repeated the interesting experiment of Mr. Faraday, as to the condensation of gases by mechanical pressure, and succeeded in converting sulphurous acid and prussic acid gases into liquids, by heating them in strong sealed tubes. During the same year he investigated the causes of the rapid decay of copper sheathing on ships, and attributing this to

*The meshes or apertures of the wire gauze ought not to be more than one twenty-second of an inch in diameter.-Brougham's Lives of Philosophers.

electro-chemical action, succeeded in preventing it, by attaching plates of iron or zinc to the copper. This, however, on being tried practically, introduced the unlooked for evil, of excessive fouling of the bottoms of ships so protected, which became liable to marine deposits in an equal manner with wooden bottoms. Davy's plan was thus rendered utterly useless, much to his mortification.

During the later portion of his life, Sir Humphry was in very infirm health, and in 1828 he determined to go abroad. Proceeding into Italy, he fixed his residence at Rome, whence he sent his last communication to the Royal Society, viz., Remarks on the Electricity of the Torpedo.' The chief peculiarity of this paper was the discovery that the electricity of this curious creature had no effect on the most delicate galvanometer. While staying at Rome, Sir Humphry was seized with a paralytic attack, which greatly alarmed his friends. Shortly afterwards he left Rome for Geneva, on reaching which city an attack of apoplexy seized him during the night, which terminated fatally. The funeral took place on the 1st of June, 1829, with all the honour and respect the inhabitants of Geneva could testify. His remains were deposited in the buryingground of the city, without the walls, the spot being marked by a simple monument, with a Latin inscription, erected by Lady Davy. Life of Sir H. Davy, by his brother, John Davy, M.D., F.R.S. London, 1839.-Memoir by Dr. Thomas Trail, Encyclopædia Britannica.- Weld's History of the Royal Society, with Memoirs of the Presidents. London, 1848. Brougham's Lives of Philosophers. London and Glasgow, 1855.

PETER DOLLOND.

Born February 2, 1731. Died July 2, 1820.

Peter Dollond, the subject of the present memoir, was the eldest son of John Dollond, the celebrated inventor of the Achromatic Refracting Telescope, who, during the greater portion of his life, was engaged in the business of a silk-manufacturer, in Stuart Street, Spitalfields. Here Peter Dollond was born and spent the early portion of his life. On reaching manhood he engaged in the same occupation as his father, and for several years they carried on their manufactures together in Spitalfields. Peter Dollond had, however, acquired some knowledge of the theory of Optics, and he determined, if possible, to turn the knowledge he had gained to the improvement of himself and his family. He accordingly commenced business as an optician, under the direction of his father, in

D

the year 1750, occupying a small house in Vine Street, Spitalfields. In 1752 John Dollond, who up till then had pursued his original occupation, grew weary of pursuits so little in accordance with the natural bent of his mind, and entered into partnership with his son, in a house near to Exeter Change, in the Strand. Here father and son began and continued that series of experimental researches which, in June 1758, led to the memorable conclusion on which was founded the construction of the Achromatic Refracting Telescope. In the following year a patent was obtained for the exclusive sale of these telescopes, but so limited were the means of the authors of this invention, that, in order to defray the expenses of the patent, they were compelled to sell a moiety of its value to an optician, with whom they entered into partnership. Notwithstanding the great practical value of this discovery, it produced little benefit for some years to the owners of the patent. In 1761 John Dollond died, leaving to his son Peter the task of carrying on the business in partnership with the optician who had paid for the patent. This connection was, however, of short duration, for the conduct of his partner was so unsatisfactory, that in 1763 Mr. Dollond purchased from him his share in the business for 2007., the full commercial value of this most important discovery being considered at that time to be worth only 400l. Peter Dollond was now in possession of the entire patent, and he was soon called upon to contest its validity with the very man who had so lately been concerned in protecting it. These suits were uniformly decided in favour of Dollond, and although vexatious in their character, were of advantage to him, not only in their immediate issue, but also in extending the name, reputation, and sale of the object whose right of ownership was contested.

Mr. Dollond now began to be more generally known, and made the acquaintance of many of the philosophical men of the time, becoming intimate with Dr. Maskelyne, the Astronomer Royal at that period, and with Mr. James Short, a man highly distinguished in arts and science. To this latter gentleman he, in 1765, proposed an improvement in the Achromatic Telescope, which Mr. Short laid before the Royal Society, at the same time signifying that it had his entire concurrence and approval. Among other works of Dollond are an improvement of Headley's Quadrant, communicated to the Royal Society, in 1772, by the Astronomer Royal; and an apparatus for the improvement of the Equatorial instrument, laid before the Society, through the same medium, in 1779.

Mr. Dollond had now earned for himself a well-deserved reputation. In 1786 the American Philosophical Society, unsolicited, and with the approval of Benjamin Franklin, elected him a member of their society.

About the year 1766 the optical business had been removed from the Strand to St. Paul's Churchyard, where it became so extensive

and prosperous, that Mr. Dollond took into partnership his brother John. For nearly forty years the brothers resided here, endeavouring, by their cordial and united efforts, to improve and extend each branch of their profession. In 1804 John, the younger brother, died, and in the following year his place was supplied by a nephew, George Huggins, who, on being admitted into partnership, changed his name to Dollond, and eventually succeeded to the whole concern. In 1817 Peter Dollond took up his residence at Richmond Hill, remaining there till June 1820, when he removed to Kennington Common, where he breathed his last, having arrived at his 90th year.-Memoir by the Rev. Dr. Kelly.

BRYAN DONKIN, F.R.S., &c.

Born March 22, 1768. Died February 27, 1855.

His

Bryan Donkin was born at Sandoe, in Northumberland. father, who followed the business of a surveyor and land agent, was acquainted with John Smeaton, the eminent engineer, from having had occasion to consult him frequently on questions relating to the bridges and other works on the Tyne. Donkin early showed a taste for science and mechanics, and when almost a child was to be found continually occupied in making various ingenious mechanical contrivances. He commenced life in the same business as his father, being engaged for a year or two as land agent to the Duke of Dorset. Donkin, however, soon showed the bent of his natural genius by quitting this agency, and going to consult Smeaton as to how he could best become an engineer. By Smeaton's advice, he apprenticed himself to Mr. Hall, of Dartford, in the carrying on of whose works he was soon able to take so active a part, that in 1801-2 he was principally entrusted with the construction of a model of the first machine for making paper, the execution of which had been put into Messrs. Hall's hands by the Messrs. Fourdrinier. The idea of this machine originated with Mr. Roberts, and formed the subject of a patent, which was assigned to Messrs. Bloxam and Fourdrinier. After considerable expense had been incurred, and many trials made with the model, the paper produced was found to be of too inferior a quality for sale. The model remained at Mr. Hall's works for some time, till at length Donkin agreed with the owners to take the matter in hand himself, and for this purpose took premises at Bermondsey (still occupied by his sons). In 1804 he succeeded in producing a machine which, on being erected at Frogmore, Herts, and set to work, was found to be successful,

although still far from perfect. A second one, in which still further improvements were introduced, was consequently made the following year and erected at Two-waters; and in 1810 eighteen more of these complex machines were erected at various mills, some of which are even now at work. The practical difficulties having been at length overcome, these machines soon superseded, both at home and abroad, the ordinary method of making paper by hand; and although the original idea was not Mr. Donkin's, still to him the credit is due of having developed, and practically introduced into general use, these most useful and complete mechanical contrivances, by means of which the process of making paper is carried on uninterruptedly from the liquid pulp to the perfect sheet ready for writing or printing.

About the year 1812 Donkin's attention was turned to the subject of the preservation of meat and vegetables in air-tight cases, and he erected a considerable manufactory for this purpose at Bermondsey. Mr. Donkin was also one of the first to introduce improvements into printing machinery. In 1813 he, in conjunction with Mr. Bacon, secured a patent for a Polygonal printing machine, and in the same year invented and brought into use composition rollers, by which some of the greatest difficulties experienced at that time in printing by machinery were overcome. Among other inventions and mechanical contrivances of Donkin's are a very beautiful screw-cutting and dividing machine; an instrument to measure the velocity of the rotation of machinery; and a counting engine for the two last gold medals were awarded by the Society of Arts. In 1820 Mr. Donkin was much engaged with Sir William Congreve in contriving a method of printing stamps in two colours, with compound plates, for the prevention of forgery; and with the aid of Mr. Wilks, who was at that time his partner, he produced the beautiful machine now used at the Excise and Stamp Offices, and by the East India Company at Calcutta.

Mr. Donkin was an early member of the Society of Arts, and became one of the vice-presidents. From this society he received two medals, one for his invention of an instrument to measure the velocity of the rotation of machinery, and another for his countingengine.

During the last forty years of his life he was greatly occupied as a civil engineer, and was one of the originators and a vice-president of the Institution of Civil Engineers, which was founded by one of his pupils, Mr. Henry Palmer, and a few other gentlemen, the Royal Charter being obtained by Mr. Telford and himself. He died in his eighty-seventh year, having passed a long life in an almost uninterrupted course of usefulness and good purpose.-From the Proceedings of the Royal Society, Nov. 30, 1855.