Royal Society. 4^ 
ftrong fpirit of fait, and fhaking it in the water, he let fall, 
into a portion of this unequally compoled mixture, fome drops of 
his folution of filver, \^hich prefently began to precipitate in a 
whitifli form, and this trial fucceeded better than if the water had 
been impregnated with but a loooth part of grofs fait ; and to purfue 
this trial farther, one drop of Ipirit of fait was diflfufed into 2000 
grains of diftilled rain-water, and upon letting fall fome drops of 
his precipitant into it, the fuccefs anfwered expe6iatioh 5 and as 
a farther trial, one grain of fpirit of fait had a raanifefl operation, 
tho' not quite fo confpicuous as the former, on above 5000 grains 
of water, whofe immunity from common fait was tried a-partj 
and that a drop of the faline fpirit, that was ufcd, did not equal 
in weight a grain of dry fait, was thus found -^ upon letting fall 
into a counterpoifed piece of glafs ten drops of that fpirit, they 
wanted near half a grain of the weight of nine grains ^ the like 
trial was made, by lubflituting above loco grains of rain-water 
inltead of the like quantity of diftilled water. 
Dr. Hook could difcover the linalleft quantity of fait contained 
in water, by means of a large poile of glafs, fomewhat of the 
fliape of a bolt- head, whole ball B, Fig. 8. Plate II. was about 
three inches diameter, but the ftem, or neck thereof, C C was not 
above f j. of an inch 5 this was fo poifed by red lead put into it 
as to make it but a little heavier than fiir or frefh water ^ then 
this poile was fufpended by the Imall ftem to the end of a (lender 
beam A, which was very tender, and would turn with a fmall 
part of a grainy this beam was hung on a fteady frame, and the 
poife hanging at one end of the fame, covered with the water to a 
certain mark, ©r division, made on the linall neck at D, it was io 
counterpoifed by Ibme fmall weights put into the oppofite icale of 
the balance F ; then the weight of the water contained in the 
ciftern, or vcffel E E, into which the poile was immeried, beinw 
firft: known, a 2000th part of its weight was taken of common 
fait, weighed out, and put into the whole 2000 parts of water 
which, by being ftirred, were diflblved^ and the poife being 
fufpended as before, near half an inch of the neck did emerge out 
of the water, more than did before the 2000th part of fait was 
diflblved therein. 
^hree ^ieries relating to Shells ; propofed by Mr. Sam. Dalf, 
md arifivered by Tir, Lifter, Phil. Tranf N° 197. p. 6'4i. 
I. TTTHAT are the Entalia of the /hops, by what authors 
VV defcribed, under what name, and how they differ from 
the Dentalia ? 
1. Of 
