143 
X, — Note on Dalton’s Determination of the Expansion 
of Air by Heat. 
By J. P. Joute, LL.D., F.R.S., &c. 
Read November 2nd, 1858. 
In the twenty-first volume of the Memoirs of the 
Academy of Sciences, p. 28, Mr. Regnault, in the course 
of a discussion of the various co-efficients given for the 
expansion of air, by different experimenters, remarks 
that Rudberg had] brought to recollection an observation 
made by Gilbert, in his Annals, to the effect that the 
experiments of Dalton and Gay Lussac, which had been 
considered as giving almost identical results, differed on 
the contrary very considerably from one another. Then, 
referring to Dalton’s experiment, related in the Man- 
chester Memoirs, vol. v. part ii. p. 599, Regnault shows 
that if 1,000 measures of air at 55° Fahrenheit expand to 
1,325 at 212°, 1,000 measures taken at 32° will become 
1,391 at 212°. Upon this he goes on to remark that 
Dalton did not appear to have been aware of the error 
which had crept into his calculations, for he says in his 
New System of Chemical Philosophy that the volume of air, 
according to Gay Lussac’s and his own experiments, being 
taken 1,000 at 32° becomes 1,376 at 212°. 
On reading the remarks of the eminent French phy- 
sicist, the extreme improbability that a man so notoriously 
exact and careful in his mathematical and arithmetical 
computations as Dalton should have made the gross error 
