Sadtler. ] 474 [April 5, 
than hydrogen and the members of the Paraflin series, assume as the basis 
of our reckoning hydrogen and any member of the Paraffin series or marsh- 
gas and any single higher member of the same series. Several of these 
possible assumptions are alluded to in my paper read February 18th, 1876, 
found in No. 97 Proceedings, p. 210, and reasons given why they were 
then rejected as not applicable. 
The reason why I was led into adopting the formulas used at that time 
are also given in the same connection. I made an error in the equaticen 
chosen to represent the contraction ensuing from the endiometric combus- 
tion, taking 3x + 2y + 3z= A, instead of $x +- 2y + 3z = A., where x 
= hydrogen, y = marsh-gas, z = ethyl-hydride and A = the observed 
contraction in volume of the gaseous mixture after the passage of the 
spark. I had used in reckoning the contraction of hydrogen the atom H 
instead of the free molecule H,. As stated (loc. cit.) I found in Fougué’s 
memoirs a confirmation of my results. The same error had evidently ex- 
isted in his mind, although it did not show as plainly, as he published no 
percentage results. After giving equations to be used on the supposition 
of a mixture of marsh-gas, ethyl-hydride, and propyl-hydride, he says: 
«Tout mélange de carbures d’hydrogene de la formule c= H’= +? doit 
remplir la condition exprimée par cette derniere equation, c’est a-dire que 
le volume de l’acide carbonique formé dans l’eudiomeétre par combustion 
doit étre éqal 4 deux fois absorption produite moins trois fois le volume 
du gaz. Le mélange de ces carbures avec Vhydrogéne libre ou avec d’au- 
tres carbures d’hydrogéne empéche cette condition d’étre realisée. Il est 
done facile deg reconnaitre si un mélange de carbures d*hydrogene gazeux 
contient exclusivement des carbures de formule ¢ H* + *.’’—(Compt. 
Rend. Vol. 87, p. 1048. 
Finding in the combustion results of all the analyses reported upon in 
my first paper an excess of contraction over that required by Fougueé’s law 
just stated above, I ascribed it (as he did in theory) to the presence of hy- 
drogen. I felt sure that I had sufficient knowledge of the details of the 
manipulation and of the errors to be avoided there, to put out of the ques- 
tion the idea that this excess of contraction might be owing to having passed. 
the spark with an insufficient supply of diluting air present with the explo- 
sive mixture in the eudiometer. The contraction was proportionally great 
too in parallel analyses of the same gas. 
I recognized, as before stated, shortly after the publication of the second 
paper, the error in the formula expressing the contraction, and saw that 
while the qualitative tests described in my first paper showed the presence 
of ethyl and propyl-hydrides, the quantitative resuits based upon a wrong 
formula would have to be revised. 
Before publishing my final revision of them, I desired to verify in the 
fullest way my qualitative absorption results before published, and to ob- 
tain, by the aid of these absorptions, material better adapted to give satis- 
factory quantitative results. This work, though unavoidably interrupted 
and delayed, I have now in hand. Without giving at present any final re- 
vision to my published analyses, I feel obliged to notice a criticism made 
