g6 Dr. Henry's Analysis of several Varieties 
water, with an equal expenditure of fuel, only 2 tons 17 cwt 
of salt can be produced.* 
Within the few past years, an attempt has been made to 
apply rock salt itself to the packing of provisions. For this 
purpose it is crushed to the proper size between iron rollers. 
The trials which have been made, I am informed, are but few, 
and the results hitherto are not perfectly known. 
The bay salt imported from foreign countries is well known 
to be prepared by the spontaneous evaporation of sea water, 
which, for this purpose, is confined in shallow pits, and ex- 
posed to the full influence of the sun and air. I have no 
addition to make to the account of its manufacture, which have 
already been given by various writers. -f 
As the results of the investigation, which forms the subject 
of this memoir, may be acceptable to many persons who can 
scarcely be expected to take an interest in a long detail of 
analytical processes, I shall present, in the following section, 
a general view of the experiments, and of the conclusions that 
may be deduced from them. In the last place, in order that 
other chemists may be enabled to repeat the analyses under 
similar circumstances, I shall describe minutely, the methods 
that were adopted, some of which are new, and others reduced 
to greater precision. If, however, in the future progress of 
science, it should appear that any of these processes are 
imperfect, it may still be admitted that, for all useful purposes, 
* See the Earl of Dundonald’s “ Thoughts on the Manufacture and Trade of Salt.” 
London, 1785. 
f Encyclop. Method. Art. Salins. (Des Marais Salans) Aikin’s Dictionary of Che- 
mistiy, II. 224. Watson’s Chemistry, Vol. II, p. 52. It is necessary to remark, that 
a great proportion of what is sold in London as bay-salt, is Cheshire large grained 
fishery salt. 
