388 Dr. Prout on 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 who may be 
inclined to take this trouble, I shall close this part of the sub- 
ject with the following remarks : 1. 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 *oi 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. 
