beaume's hydrometers. 
3 
make use of that liquid for determining the 66° of their standard, 
and, therefore, are safe in dividing the space between this level 
and that of water into 66 equal parts. Unfortunately, the author, 
instead of mentioning the corresponding sp. gr., contents himself 
with asking, " But was this proof acid well concentrated, and was 
Guyton's hydrometer properly constructed V 9 when he must have 
known thai concentrated oil of vitriol has a density of at least 
1.830, (which is so stated in an article in the same work only a 
few pages back,) while the tables he publishes further on give 
1.7674 as = 66°, showing that at that time the same discrepancy 
existed between the pese in general use, and the tables of com- 
parison as at the present day. 
The modern p&se esprit and pese acide are entirely different in- 
struments from those invented by Beaume. The density of a solu- 
tion containing 15 per cent, of salt is 1.1094, as determined by 
Francoeur and others, and which I have verified by experiment. 
Then as the bulk of the hydrometer immersed in liquid is inversely 
as the sp. gr. of the liquid, it follows that the portion of the hy- 
drometer above water bears the same ratio to its total bulk, that 
the increase of sp. gr. of the liquid over water does to its real sp. 
gr. If then the interval on the stem is made equal to a certain 
number of degrees, the value of any other degree may be readily 
obtained by the equation (for the total number of degrees 
contained in the volume of the hydrometer,) and |i for any given 
degree, or if the sp. gr. is known and the degree sought for 
q. I n the above equations d = greatest sp. gr., a = least 
sp. gr., or zero, H — value of hydrometers in degrees, and 
q — the given degree. Making then, d = 11094 the equation gives 
1 1094 * 15 = 159° =H and as the formula for Beaume's 
1.10U4 -1.000 1<J ^ X1 dllU 153- q 
original pese acide. 
Professor R. 0. M'Culloch in his admirable " Report on Hy- 
drometers," has given tables by Francoeur calculated from the 
above formula, but which are useless for reference, as the degrees 
do not correspond with those given by any of the modern hy- 
drometers ; for example, making 66° == sp. gr. 1.767, instead 
of 1.83, which is the sp. gr. of commercial oil of vitriol, requiring 
69|° to equal sp. gr, 1.83. As the scale upon which 66° =1.83 
has been for many years in such general use, it would be impossi- 
