264 Biographical Account of [AprRir, 
years ago that the lead which lines tea boxes contains about four 
per cent of tin. Zinc produces the same effect upon lead; but not 
bismuth or silver. The order in which the colours appear on melted 
lead is as follows: yellow, purple, blue—yellow, purple, green— 
pink, green—pink, green. 
V. Observations on the Sulphur Wells of Harrogate, made in July 
and August, 1785. (Phil. Trans. 1786.) 
In this paper Dr. Watson describes the situation of the four 
Harrogate wells, their specific gravity, and the experiments which 
he made to determine their saline and gaseous ingredients. In the 
present state of our chemical knowledge of mineral waters, it 
would be useless to state the result of these experiments. It may 
be sufficient to say that the author’s opinions were accurate as far 
as they went; that he knew of the existence of sulphureted 
hydrogen, and that it could be obtained by the solution of certain 
metallic sulphurets in muriatic acid. 
= 
In the year 1781 Dr. Watson published his Chemical Essays, in 
three 8vo. volumes. ‘This work was highly popular at the time of 
its appearance, and contributed very materially to produce that 
taste for chemical science which at present so generally pervades 
Great Britain. These essays are beyond dispute the most elegant 
work on chemistry which has appeared, either in this country or 
the continent of Europe. Though the science has undergone 
two complete revolutions since 1781, and though the progress 
which every branch of it has made since that period is quite enor- 
mous, yet these essays have not yet lost their interest, and will 
always retain a considerable portion of value, because they contain 
a great collection of historical facts not to be found any where 
else. The essays on gunpowder, on the saltness and temperature 
of the sea, on the quantity of water evaporated from the surface of 
the earth in hot weather, on the smelting of lead ore, on silver ex- 
tracted from lead, and on red and white lead, may be still perused 
with interest by the chemists of the present day, and deserve to be 
studied as models of elegant memoirs on scientific subjects. It 
would far exceed the limits to which J must confine myself here, 
were. to attempt an analysis of the contents of these volumes. 
But I consider the task as quite unnecessary, as they must be 
familiar to every chemist of taste in the British empire. 
{n the year 1786 he published a fourth volume of Chemical 
Essays, which I consider as much more valuable than the preceding 
ones. It contains a great stock of very valuable information re- 
specting the progress of various chemical manufactures in Great 
Britain, chiefly concerning the smelting of some of the metals, and 
forming some of the most tmportant alloys. His account of blende, 
zinc, brass, gun-metal, tinning copper and iron, and gilding in or 
moulu, are highly interesting. To this volume he soon after added 
a fifth, containing his essays which had been published in the Philo- 
