August 2, 1889.] 



SCIENCE. 



69 



In charging a secondary battery from a dynamo, there is need 

 of maintaining the charging current at a constant and suitable 

 strength. For this purpose it will be seen in Fig. 2 that the dy- 

 namo is supplied with a clock-work arrangement, to one of the 

 shafts of which the dynamo brushes are attached. Now, so long 

 as the current strength is maintained, this clock-work remains 



FIG. 4. — AUTOMATIC RHEOSTAT AND REGULATOR. 



still; but upon any slight variation the contact-bar in the regula- 

 tor (seen in the upper part of Fig. 3), consisting of a solenoid 

 carrying a core with the contact-bar at its low end, closes a circuit 

 passing through one or the other of the magnets of the dynamo 

 clock-work, and causes this to move the brushes so as to increase 

 or decrease the current, as need may be. 



Again, to avoid the reversal of the polarity of the dynamo 

 through an excessive fall in its current while charging the battery, 

 which would allow of a reverse current passing through it from 

 the storage-battery, the apparatus shown on the lower part of 

 Fig. 3 is provided. On the occurrence of any sudden change, the 

 lever shown near the bottom of the board would fall, breaking the 

 main circuit, and causing the alarm-bell at the top to ring. 



The practice of Mr. Knowles in charging is to start the dynamo 

 on the resistances contained in the rheostat (Fig. 4), connecting 

 the batteries when the due strength of current is reached, when, 

 at the same time, the automatic contrivance shown on the top 

 cuts out resistance in proportion. 



The battery station in this Brooklyn plant is about half a mile 

 from the dynamo station, but could be much farther away, it is 

 maintained. Here the cells (Fig. i) are arranged in batteries, as 

 shown in Fig. 5. These racks are of wood, covered with insulat- 

 ing paint. Each cell rests on porcelain knobs, and the whole is 

 again insulated from the floor. 



In his secondary battery Mr. Knowles has several new features, 



and has avoided the application of the active material as a paste. 

 Fig. I shows the cell complete. The perforated plates of non- 

 oxidizable alloy are made in two sheets, between which is held a 

 layer of the active material, which is moulded to the right shape 

 before being placed between the two halves of the retaining plates. 

 When ready, the whole is assembled as shown in the illustration, 

 flexible insulating-rods being passed through the hooks cast on the 

 plates top and bottom. 



In a later number we hope to give further details of this system, 

 which is being introduced by the Mutual Electric Company of 

 Brooklyn. 



DESCRIPTION OF FERRET MOTORS AND DYNAMOS. 



The chief distinctive feature of these machines, manufactured 

 by The Elektron Manufacturing Company, Brooklyn, N.Y., is the 

 method of constructing the field-magnet, whereby the well-known 

 advantages due to lamination and to the best quality of iron are 

 secured, while the cost, which has heretofore been a bar to the 

 commercial use of such magnets, is reduced nearly to that of for- 

 gings. This method of construction is peculiarly adapted to 

 machines of small size ; and by its use their efficiency is greatly 

 increased, as a test will show. It may also be used to advantage 

 in machines up to 10 horse-power, and even higher ; as, by the in- 

 genious shape and arrangement of the plates, a magnet of large 

 size may be built up of comparatively small plates, which are 

 stamped from sheet iron, no other machine-work being necessary. 

 Eight sizes are now on the market, and others will be soon brought 

 out. 



In the ^L, i, and J horse-power sizes, a magnet of the ordinary 

 U-shape is used, in which the plates are so formed and put to- 

 gether that the limbs may be swung apart and clamped to the face 

 plate of a lathe for winding, after which they are swung back and 

 bolted fast. Fig. i shows one of these motors complete. Fig. 2 

 shows the magnet before winding. 



In machines of i horse-power and upwards, the double horse- 

 shoe shape, with consequent poles, is used. These are shown in 

 Fig. 3. Upon removing the two bolts which pass through the 

 yoke, the top half of the magnet may be separated from the lower 



half. Each half is then attached to a lathe or other suitable ma- 

 chine, and wound by revolving it, after which they are put together 

 and the bolts replaced, all these operations being very simple and 

 very rapidly done. 



One of the plates of which these magnets are built is shown in 

 Fig. 4. Four of these are necessary to form the complete enclos- 

 ure (see Fig. 5). It will be noticed that the plates interleave at the 

 yoke, at which point their gross-section is enlarged, and they are 



