141 
of EdinhurgJi, Session 1882-83. 
By this arrangement the sulphuretted hydrogen is preserved from 
oxidation, and can always 
he run off perfectly clear. 
The gas tap should as a 
rule be kept closed, and 
need only be opened for 
an instant when the sul- 
phuretted hydrogen water 
ceases to flow. It should 
be well oiled but not 
greased. 
The only objection, if 
any, that I have been able 
to discover to this method 
is that after a time the 
smell of the sulphuretted 
hydrogen water becomes 
somewhat altered in char- 
acter, apparently owing to 
the formation of traces of 
some organic sulphur com- 
pound, the nature of which 
I have not yet been able to examine. 
2. On the Thermo-electric Position of pure Cobalt. By 
Professor Tait. 
3. Transmission of Power by Alternate Currents. By Prof. 
George Forbes. 
When a current of electricity is sent through a dynamo machine 
in the same direction as the current flows when the dynamo is being 
used as a generator, then the field magnets are polarised in their 
normal manner, and the magnetism of the armature is such as to 
cause it to rotate in the opposite direction to that in which it turns 
when generating a current. The dynamo now acts as a motor. 
If now the current be sent through the dynamo in the opposite 
direction, the field magnets are polarised in the opposite manner, 
^.e., a north pole is found where a south pole was before. The same 
is true of the magnetism of the armature. Hence, in this case the 
