388 Dr. Prout 071 the ultimate composition^ ^c. 
as these appear to do, cannot be too firmly established; I 
therefore, in the mean time, earnestly invite chemists in 
general to repeat them, and thus either to confirm them, or 
point out their errors ; and for the sake of those tvho may be 
inclined to take this trouble, I shall close this part of the sub¬ 
ject with the following remarks : i. The multiples of hydro¬ 
gen, carbon, and oxygen, are assumed in the preceding 
calculations as i : 6 : 8. 2. The results given are, on all 
essential points, the means of many experiments, the differ¬ 
ences among which are either inappreciable, or at most vary 
from *01 to *03 of a cubic inch in from 5 to 8 cubic inches 
of carbonic acid or oxygen gas; the greatest differences in 
general, being for obvious reasons, found among meror- 
ganized bodies; and hence the analyses of these are usually 
stated to the first decimal figure only, 3. As rules to be 
observed, I would say, that a single result should never be 
registered, nor a single calculation made, till the operator has 
made himself complete master of his apparatus, and carefully 
studied the nature of the substance to be analyzed ; for dif¬ 
ferent substances often require very different management: 
that two or three results should never be relied on; the 
minute quantities here sought can be only obtained, like those 
of astronomy, by repeated observations: and lastly, the 
utmost care should be taken that the substances operated on 
be pure^ a point of greater importance, and frequently of 
more difficult accomplishment than any other, and one that 
has caused me more trouble than all the rest put together. 
