140 
base. Moreover, long experience has proved that for the 
production of electric light the alternating current is greatly 
superior to the continuous one, as commutators are dis- 
pensed with, and it has the important advantage of con- 
suming the carbons equally, and thereby always retains the 
luminous point in the focus of any optical apparatus used 
in connection with it. 
In short, M. Gramme, in his endeavour to reconcile the 
incompatible relations of the voltaic current and the 
magneto-electric wave at the instant of its generation, has, 
by inverting the order and functions of the organic parts 
of an ordinary magneto-electric machine and suppressing 
the action of a number of the armature helices, brought 
about results retrogressive from those previously attained 
by Nollet, Berlioz, and Holmes, and it is only by the 
adoption of the principle of electro-dynamic accumulation 
(i.e., the exciting of a major electro-magnetic induction 
machine by a minor one, fixed on the same base), in accord- 
ance with the principles laid down by the author in his 
former papers, that the results obtained by M. Gramme 
exceed those from ordinary magneto-electric machines. 
PHYSICAL AND MATHEMATICAL SECTION. 
April 22nd, 1873. 
Alfred Brothers, F.R.A.S., President of the Section, in 
the Chair. 
Results of Rain Gauge Observations made at Eccles, near 
Manchester, during the year 1872, by Thomas Mackereth, 
F.R.A.S., F.M.S. 
The characteristic of the rainfall of the past year is its 
