are near the corresponding armatures of the nearest drum, and to break it when the parts are in their nearest position to each other. Fig. 39, which is a plan of this machine, gives a very good idea of this arrangement, which, however, has not given results superior to other similar direct-acting motors.

The same year, 1848, Froment constructed several other motors, as shown in Figs. 40 and 41, of which one was named by its inventor a wedge electromotor. In this machine there are four electro-magnets, fixed opposite one another in pairs, and slightly inclined from the horizontal, and the armatures are in the shape of elongated wedges, which work vertically in

grooves, which guide them in their upward and downward motion. They are each fitted to a connecting-rod working on a crank shaft, on which is a fly-wheel and eccentrics acting as commutators. These two wedges are, of course, so arranged that when the attraction on one commences that on the other ceases, and vice versa. When one of the

wedges is at the top of its stroke, its two angular faces are at their maximum distance from the magnetic poles, and it is then that the current excites the electro-magnets; these then draw the wedges down till their thickest part is in the axial line, when the current is broken in these electro-magnets and sent by the commutator into the others, which are then in the position originally occupied by the first set, thus continuing the action. In this case the attractive effect is tangential, and is the result of both lateral and direct attraction; however, no special advantage has been derived from this arrangement.

We show, at Fig. 41, the large direct-acting rotary motor, which Froment constructed to work the dividing machines in his laboratory. All the electro-magnets were fixed vertically, one above another, on six iron uprights, forming the sides of a very solidly built hexagonal prism. In the centre of this cylindrical case, bristling with electro-magnets, was placed the rotating shaft, having throughout its length a series of vertical armatures placed end to end, and arranged to correspond with each of the pairs of bobbins. This shaft terminates above in a

wheel, which, acting on another of equal diameter, worked the commutator seen on the left of the figure, and also cogged wheels to reduce the speed of the pulley on the right, by which was worked the necessary machines.

The commutator was composed of a double set of wheels round the axis of the shaft, pressing on plates alternately insulating and conducting, joined to the different sets of electro-magnets.

It was said that this motor had a force of threequarters of a cheval vapeur, but Froment often said that the power was much less than this, notwithstanding the alterations he made in this motor in 1862.

Such are the motors of M. Froment which for so long were regarded as perfect, and which cost their author much time and money. He, however, never had great expectations with regard to this application of electricity, and I have often heard him express his doubts as to the future thereof. Certainly, the most ingenious mechanical contrivances had been made use of in this type of machine, but the physical effects to be dealt with were not then so perfectly understood as at present, and it is only recently that any favourable results have been obtained, and that in quite a different direction.

Page's Machine.-This machine, brought out in 1850, was founded on a property then little known, namely, the attraction of solenoids, which has since furnished several important types of machines. We have mentioned on p. 14 this sort of

attraction and its advantages; unfortunately, the force developed is slight, and it is only with great reserve that we can accept the results announced by the newspapers of that time, results which were summed up as follows in the American paper, 'The National Intelligencer' :

"Professor Page, in the course of lectures delivered by him at the Smithson Institute, has shown that before long electro-magnetic action will have dethroned steam and will be the adopted motor. He has, to convince his audience, shown some most astonishing experiments. An immense iron bar weighing 160 lbs. was lifted by the electro-magnetic action, and was rapidly raised and lowered, dancing in the air like a feather, and without any apparent support. The force acting on the bar was estimated at about 300 lbs., although it was exercised through a distance of ten inches. One can hardly form any idea of the noise and brilliancy of the electric spark when it is drawn from a certain part of the great apparatus; it is a regular pistol shot. At a little distance from this point the spark makes no noise.

"The professor also showed his machine of four or five horse-power, worked by a battery contained in a space of about 3 cubic feet. It is a double-acting machine, with a two-feet stroke, and the whole thing, engine and battery, weighs about a ton. When the motive power is connected the engine works admirably, making 114 revolutions a minute. Applied to a circular saw of 16 inches in diameter, which cut into strips planks of 1 inch in thickness, it made