OBITUARY NOTICES OF FELLOWS DECEASED. Dr. Lawrence Holker Potts one of the original Membersof this Society was born in London on the 12th of April 1789. His father was a medical practitioner in Pall Mall. At an early age he was for a short time at Westminster School from which he was removed to Northamptonshire where he finished his education. Being designed for the medical profession he was apprenticed to a gentleman in Warwick after which he became a house pupil to Sir Benjamin Brodie for two years. In 1812 he passed his examina- tion as a surgeon and was appointed to the Royal Devon and Corn- wall Militia. On this regiment being disbanded in 1814 he settled at Truro pursuing as his leisure time would admit his favourite studies in chemistry and mechanics.With the mineralogy of Corn- wall he was well acquainted and possessed a fine collection of cabinet specimens some of the best of which were lately presented to Prince Albert for the Prince of Wales. In 1818 Dr.Potts in conjunc- tion with other gentlemen originated the Royal Institution of Corn-wall and to its advancement he devoted as much of his time as could be snatched from his professional engagements. In 1825 he took his degree of Doctor of Medicine and in 1828 was appointed superin- tendent and physician to the Cornwall Lunatic Asylum. Froni this position he removed to London and having taken a lease of Van- burgh Castle Blackheath opened it as an establishment for the treatment of spinal diseases in young ladies. Among his numerous manuscripts is a work nearly complete on spinal complaints.It was shortly after this period that he made his great discovery for sink- ing tubes cylinders or coffer-dams by atmospheric pressure ; and the time and attention required to bring this invention into prac- tice obliged him at a great pecuniary sacrifice to relinquish his previous undertaking. This invention although highly approved by the Trinity Board the Lords of the Admiralty and other highly influential parties required a long and impoverishing struggle to OBITUARY NOTICE OF DR. POTTS. 347 bring it into extensive operation and he just survived to see the likelihood of its important application under the able management of Messrs. Fox and Henderson when he expired after a long and painful illness on the 23rd of March 1850.The beautiful adaptation of atmospheric pressure which forms the subject of Dr. Potts’s invention was first tried by him on a large scale on the Goodwin Sands on the 16th of July 1845 when an iron tube 2feet 6 inches in diameter was driven into the sand to a depth of 22 feet in two or three hours; the greatest depth at- tained has been 70 feet. The method of operating is to place the tube or cylinder in a perfectly vertical position resting on the bed of the river or sea bottom. By means of a cap and an elastic tube this is connected with an exhausted receiver and on the communica- tion between the two being opened the pressure of the atmosphere on the surface of the water produces such a rush to fill the vacuity in the interior that it carries on a constant excavation under the lower edge of the tube which rapidly sinks by its own weight aided by that of the surrounding air; this operation is repeated as often as necessary fresh lengths of tube being added as required until a rocky or firm foundation is reached; the contents arc then pumped out and the interior filled with concrete or when of sufficient magnitude with solid brickwork or masonry.If any impediment is met with the apparatus can be readily converted into a diving-bell by simply reversing the action of the air and the men can work dry within the cylinder until such obstruction has been removed. By this means beacons have been erected by the Trinity Board on the Mar-gate the Girdler the Shingly the Buxhey and other sands lying at the mouth of the Thames; and also several of the railway bridges as at Huntingdon and Peterborough on the Great Northern Rail- way; the bridge over the Thames at Windsor ; the new bridge over the Medway at Rochester ;and one over the Shannon the cylinders of which are 10 feet in diameter and were carried through several feet of yellow clay.In Cornwall a shaft has been sunk at Wheal Ramoth Mine under the sea by this means. Dr. Potts was an ardent lover of science and his devotedness to its cause was constant and persevering. James Thomson Esq. F.R.S. was born at Blackburn on the 6th of February 1779. His family were nearly connected with that of the late Sir Robert Peel. At the early age of fifteen he went to pursue his studies at Glasgow.There he entered into relations of VOL. 1V.-NO. KVI. BB OBITUARY NOTICE OF JAMES THOMSON ESQ. confidential friendship with Gregory Watt (son of the immortal improver of the steam-engine) after whose early death he remained OIL terms of intimacy with James Watt himself and Thomas Camp b ell author of the “Pleasures of Hope,” whose distinguished poetical genius he early felt and appreciated. After remaining at college a year he entered the mercantile house of Joseph Peel and Co. in London. In this capital be resided for six years associating with the most remarkable literary and scientific men of the age. Sir Humphrey Davy Wollaston and Porson were amongst his intimate friends. His knowledge of the then little cultivated science of chemistry attracted the notice of his employers who thinking it might be rendered more available in the manufac- tories of Lancashire than in a London counting-house removed him to their establishment near Accrington.Here he remained nine years having in the meantime married Cecilia eldest daughter of the Rev. Thomas Starkie Vicar of Blackburn. In the year 1811 he established himself at Primrose near Clitheroe where he pursued the occupation of calico-printing for nearly forty years. Notwithstanding the claims and difficulties of an arduous business he devoted much time to the cultivation of general science and lite- rature. He was besides a generous patron of the arts and a liberal contributor to all public institutions.His power as a writer is well known to all his acquaintances and it is much to be regretted that he has left behind him no further specimens of his talent for compo- sition than are comprised in a few short though masterly pamphlets. His scientific knowledge and highly cultivated taste combined with the great energy and enterprise of his character placed him in the very foremost rank amongst the distinguished and philosophical manufacturers of his time; and in the neighbourhood where he resided and to the prosperity of which he may be considered as having so largely contributed his name will long be remembered with gratitude as a friend and benefactor. In Davy’s Chemical and Philosophical Researches on Nitrous Oxide published in 1800 he gives some observations received by letter dated October 28th 1799 from his “ingenious friend Mr.James Thomson,” relating to the composition of. nitrous acid who from experiments therein alluded to considers that ‘‘nitrous acid is nothing more than nitric acid holding iiitrous gas in solution.” The accuracy of these views is not a question for consideration npw but it will fully illustrate the originality of Mr. Thomson’s talents and the estimation in which he was held by so eminent a philosopher as OBITUARY NOTICE OF JAMES THOMSON ESQ. Sir Humphrey Davy. From the same work we learn that Mr. Thomson was one of the first in association with Southey Cole- ridge and other intimate friends of Davy’s to inhale the nitrous oxide gas an account of the effects of which are given in a letter con- tained in the appendix to this work.In cc Nicholson’s Journal,” for 1809 p. 174 we find a paper “On the Analysis of Sulphate of Barytes,” by Mr. James Thomson which contains analyses not only of the sulphate but also of the carbonate and nitrate of barytes as also of sulphate of lime. By comparing his results with those now generally considered as accurate it will be found that very little dif- ference exists. About the year 1822,Mr. Thomson commenced his investigation of the mummy-cloth of Egypt which had up to that period been considered as consisting of cotton. After various experi- ments to determine this point he states ‘‘It occurred to me that the supposed unfitness of cotton lint compared with linen for dressing wounds had been accounted for by the different form of their fibres the one being sharp and angular and the other round and smooth; and in fact I found in the twelfth volume of the Phil.Trans. for the year 1678 this structure ascribed to them by that early microscopic observer Mr. Leuwenhoek. It seemed to me therefore that the most simple mode of distinguishing between cotton and linen would be to subject the Jibres to examination under a powerful microscope. Not being possessed of such an instrument or accustomed to its management my friend Mr. Children undertook through Sir Everard Home to solicit the assistance of Mr. Bauer. I transmitted to himvarious pieces of cotton and linen both manufactured and in their raw state as well as fibres of unravelled mummy-cloth and received from him a letter dated September 16th 1822 in which he pronounced every specimen of mummy-cloth subjected to his examination to be linen.” We have been more particular in giving these details as a claim of priority to this discovery has been set up by other parties.Mr. Thomson was still occupied during the few leisure hours he could command from the engagements of his extensive establishment at Primrose and his infirm health would admit in a long-pending dis- cussion on this subject with some Italian philosophers up to the time of his decease. These results have been as yet but partly published the manuscripts and drawings for the completion of the subject being in the hands of his son-in-law Dr. Braun.