to entire satisfaction. Early in the following year, two foreigners made an attempt to gain a patent for the new bleaching process; but they were opposed by Mr Watt and Messrs Cooper and Henry of Manchester, all of whom had already bleached by Berthollet's method. Notwithstanding the misrepresentations in several histories of bleaching, it is manifest from these facts as well as from the dates of several letters of Mr Watt and Mr Henry, that the great improver of the steam engine, had also the honour of introducing the process of bleaching by chlorine into Great Britain; and though he was not the original
discoverer, yet he greatly simplified and economised the process of obtaining the discharging agent employed, and the vessels and other arrangements used in the art of bleaching. Among other improvements may be mentioned his
method of testing the strength of the chlorine liquor, by ascertaining how much of it is necessary to discharge the colour of a given quantity of infusion of cochineal. The benefits which Mr Watt conferred on chemical science, did
not terminate here. From a letter written to Dr Priestley in 1783, and in another to M. De Luc, in the same year, he communicated his important discovery of the composition of water. But in the beginning of the following year, Mr Cavendish read a paper on the same subject, claiming to himself the nonour of discovery; and in the histories of chemistry, the claims of Cavendish are silently admitted. There is a confusion of dates in the documents on this subject, which at the present day it is impossible to reconcile; but from the
characters of the two men, we are inclined to think that each made the discovery independently of the other, and that therefore the credit is due to both. Mr Watt's letter to M. De Luc was read before the Royal Society, and published in their Transactions for 1784, under the title of "Thoughts on the Constituent parts of Water, and of Dephlogisticated Air; with an Account of
some Experiments on that subject." Mr Watt also contributed a paper on the medical properties and application of the factitious airs, to the treatise of Dr Beddoes on pneumatic medicine, and continued during the latter period of his life deeply to engage himself in chemical pursuits.
A patent was granted to Mr Watt in 1780, for a machine for copying letters and drawings. This machine, which soon became well known, and exten- sively used, was manufactured by Messrs Boulton and Kier, under the firm, of James Watt and Company. He was led to this invention, from a desire to abridge the time necessarily spent in taking copies of the numerous letters he was obliged to write. It was constructed in two forms, on the principle of the rolling press, one of them being large, and fitted for offices; the other light, and capable of being inclosed in a portable writing desk. Through the course of the following year, Mr Watt invented a steam drying apparatus, for his friend, Mr M'Gregor, of Glasgow. For this machine he never took out a patent, although it was the first thing of the kind ever contrived; nor was there ever any drawing or description of it published during his lifetime.[1] During the winter of 1784, Mr Watt made arrangements for heating his study by steam; which method has since been extensively applied to the heating of private houses, conservatories, hot-houses, and manufactories. Concerning the history of this apparatus, it is but justice to state, that colonel Cook had, in the Philosophical Transactions for 1745, described a method of "heating apartments by means of the steam of water conveyed along the walls by pipes;" but there is no proof that this was known to Mr Watt.
In the year 1800, Mr Watt withdrew from the concern at Soho, delivering his share of the business to his two sons, James and Gregory, the latter of whom died in the prime of life, much regretted by all who knew him. After
- ↑ See Edinburgh Encyc. xviii., Steam Drving.
