426 Dr. Blagden’s Supplementary Report 
calcined by exposure to the air. In order to try whether 
this circumstance made any difference in the quality of the new 
spirit, Mr. Gilpin mixed some of it with an equal weight of 
water, and afterwards brought the mixture to all the different 
temperatures from 30° to ioo°, operating in the same manner 
as he had done with Dr. Dollfuss’s spirit ; when the specific 
gravities were found to come out the same. Mr. Schmeisser’s 
alcohol, therefore, was used without hesitation. As no censure 
had yet been passed on our former experiments, the same 
general method was pursued for the new series ; with a small 
variation, however, the reason of which is now to be ex- 
plained. 
In the Report on the first experiments I introduced the 
following remark. “ It must be observed, that Mr. Gilpin 
“ used the same mixture throughout all the different tem- 
“ peratures, heating it up from 30° to ioo° ; hence some 
“ small error in its strength may have been occasioned, in the 
“ higher degrees, by more spirit evaporating than water ; but 
“ this, it is believed, must have been trifling, and greater in- 
“ convenience would probably have resulted from interposing 
“ a fresh mixture/’ The consciousness that such a source of 
error existed, made us desirous of ascertaining to what quantity 
it amounted, by some previous experiments, before the new 
set should be begun. These shewed that it was somewhat 
greater than had been supposed, though not such as ever 
to cause a difference of more than a single unit in the third 
place of decimals, even in the temperature of ioo°. 'The 
greatest difference found, in that degree of heat, was ,00094 ; 
and in a heat of 8o°, the highest to which the tables for use were 
to be carried, it amounted only to ,00064 ; being in both cases 
