Fan. 5, 1882] 
NATURE 
227 
one of the newest and most interesting is Dr. Hopkin- 
son’s electric elevator or “lift.” 
But to come back to the application of power on the 
very small scale adapted for domestic purposes ; several 
small motors exist, each of which can do excellent work. 
The earliest of these small modern motors is that of M. 
Marcel Deprez, invented about three years ago, and 
which consists (see Fig. 2) of a single Siemens arma- 
ture, AB, of the old well-known type, placed longitudi- 
nally between the poles of a horse-shoe, or rather a U- 
Fic. 2. 
shaped steel magnet. The advantage of this arrange- 
ment is that the position of the armature utilises the 
whole field of force which lies between the limbs of the 
magnet. A large number of these little motors were set 
up by M. Marcel Deprez at different points of the 
galleries of the late Paris Exhibition in illustration of the 
possibility of distributing power from a central source. 
Two other forms of motor have more recently claimed 
attention, The first of these is the invention of M. Trouvé, 
and differs from that of M. Marcel Deprez in having an 
electromagnet instead of a permanent :steel magnet to 
produce the field of magnetic force within which the 
armature is placed. The armature is also longitudinal 
and of the Siemens’ type, with a slight modification, 
suggested by M. Trouvé, with the purpose of getting a 
more continuous action. 
Fig. 3 shows how such a little motor may be attached 
Fic. 3. 
to a sewing machine. The axis of the armature is here 
vertical and carries a small disk or wheel of india-rubber 
which, when the motor is clamped in position, presses 
against the driving wheel of the sewing machine with a 
contact sufficient to enable it to drive the machine; a 
Fic. 4. 
work which in spite of the small dimensions of the motor it 
accomplishes readily, on account of the high speed with 
which it runs. No steam-engine so small could possibly 
do the work without great loss, since steam will not give 
up its heat at an indefinitely great rate. It is said that 
three of Faure’s accumulators weighing 50 Ibs, each may, 
when fully charged, drive a sewing machine by a Trouvé 
motor for a whole week, working five or six hours every 
day. Motors similar to this have been fixed by M. 
Trouvé in his little electric canoe, and are suggested by 
M. Tissandier for balloon steering. ; 
The favourite motor, however, at the present "time 
appears to be that of Griscom, an American electrician, 
whose English agent is Mr. Paterson of Little Britain, 
and which we depict in Fig. 4. This elegant little 
machine is only 44 inches long, and weighs a little over 
two pounds only. But it is remarkably powerful and 
steady in its action. It can, when fed with a current of 
