38 
Dr. Meld on's Electric Motor. 
[January, 
The armature of the new machine is formed by joining 
together two 15-inch solid pulley wheels, with seven flat bars 
of iron, each bar being 24 inches long by 3 inches wide, 
and inches thick, and, as has been observed, the bars are 
laid upon gutta percha, copper bolts being used to fasten 
them to the wheels. A shaft of i^-inch steel passes 
through the centre, and the whole is supported by a hard- 
wood frame, stayed with iron. Each side of the frame, 
where the shaft emerges therefrom, is supplied with an 
ivory commutator, the one on the right having three, and 
the other four, brushes, each of which communicates with 
a magnet. Attached to the frame are seven elecfiro-magnets ; 
the three larger ones being made of 2-inch soft iron, and 
wound with No. 14 wire, without bobbins, and the other 
four of inch iron, and wound with No. 11 wire. The 
total weight, as at present constructed, is a little over 
3 cwts. The first trial of the motor took place in July last, 
in a boat 22 feet long and 5 feet beam ; and the battery used 
on the occasion consisted of thirty-six cells of bichromate of 
calcium, with zincs 6 by 4 inches, and carbons 6 by 5 inches, 
the latter, as will be observed, being larger than the former. 
Half of the cells passed through a commutator into one set 
of magnets (the whole charge going into one magnet at a 
time), and the remainder of the cells, through the other 
commutator, into the second set. The great utility of this 
arrangement was experienced during the trip, as when all 
the cells were made use of the boat went at full speed, but 
when only one commutator was employed half-speed was 
obtained, and on a long trip the second battery could, of 
course, be re-charged. The motor is capable of making 
about goo revolutions a minute, but this in the trial trip 
was reduced to 400, when the boat went over, with a slack 
tide, g miles in a little more than one hour, a single mile 
having been accomplished in seven minutes, and subse- 
quently, when the tide was more favourable, 11 miles were 
gone over in an hour. A little over two-horse power has 
been registered from only twenty-four cells ; and here it may 
be remarked that Dr. Meldon, who takes an unusual interest 
in anything that relates to this science, has managed, by a 
very simple contrivance, to get over the difficulty hitherto 
experienced in keeping up a continuous light for many 
hours : that gentleman has had five Swan lamps in his 
house during the past two winters, and he makes his bi- 
chromate cells last twelve hours, by using large zincs and 
carbons, which at first are only immersed a short distance 
in the fluid, and then after two hours lowered a few inches 
