On Atomic Arrangement in Compounds. 5d 
say more of the advantages which it offers to the demonstrator 
of physics. Itis, however, perhaps not superfluous to remark, 
that the apparatus is so little costly that any institution at 
which instruction in physics is given may be able to obtain it. 
A bellows and wind-chest for organ-pipes and a siren belong 
to the necessary apparatus of instruction in acoustics; we 
require in addition only a small piece of apparatus which may 
easily be fitted to any siren. The lever arrangement must, 
however, be well made, so as to avoid disturbing noises, which 
might easily be produced by the friction of the lever against 
the revolving wheel. 
The apparatus for my own experiments was made by the 
University apparatus-maker, Herr Engel, of Marburg. 
VI. The Influence of Atonic Arrangement on the Physical 
Properties of Compounds. By W. N. Hartizy, £.B.S., 
Professor of Chemistry, Royal College of Science, Dublin*. 
N the Philosophical Magazine for March 1882, Dr. 
Carnelley states that Professor Julius Thomsen, of Co- 
penhagen, has concluded from the heat of combustion of 
benzene that the six carbon-atoms in the compound “are 
not bound by three double and three single linkings, thus, 
Bruhl, however, as we shall see presently, concludes from the 
* Communicated by the Author. 
