43^ Dr. Blagden's Supplementary Report 
required ; of their preference in other respects, the practical 
officers who are to use them will probably be found the best 
judges. That which can be managed with the greatest faci- 
lity and quickness, which affords the least opportunity of 
making blunders, which is least liable to be out of order, and 
shews most immediately if it be so, will unquestionably prove 
the most satisfactory in practice. Hydrometers having a ther- 
mometer inclosed within them must be condemned, as not ascer- 
taining the temperature with the requisite precision. An at- 
tempt to supersede the use of the thermometer, by employ- 
ing for the hydrometer, a substance which “ has the same 
“ degree of expansion as the mean of the compounds/’ is very 
inconsistent with the kind of accuracy sought by these expe- 
riments. 
As an allowance is made, in our table of specific gravities, for 
the expansion and contraction of the glass weighing-bottle, this 
must be taken into the account, with every areometer, when- 
ever much exactness is desired. 
I am still of opinion, that the best way of laying the 
duty would be directly on the quantity of alcohol contained 
in any composition ; and though this might require too great 
a change in the present system of laws, yet as the same prin- 
ciple may be applied in estimating the strength, and taking 
stock, I will just mention in what manner the computation can 
be most readily made. From the numbers in this Supple- 
mentary Report a table must be constructed, on the top of 
which shall stand every degree of heat from 40, or 30, to 80, 
and at the side every specific gravity from ,823 to 1,000, if it be 
thought necessary, or as much less as will answer the purpose. 
The places of this table are to be filled up, by computing, from 
