April 6, 1883.] 



SCIENCE. 



243 



frame of the machine, eight very powerful 

 compound permanent magnets, each composed 



brought together, in two groups, to the four 

 brass collecting-disks, i, which are mounted 

 in pairs on an insulated bush, J, fixed to 

 the principal shaft of the machine. The 

 1 ■ details of the collecting-apparatus are 

 shown in Figs. 24, 25, and 26. Against 

 the disks, i, are pressed, by means of 

 springs, the four collecting plates or 

 brushes, K' K', which are in metallic 

 connection with the attachment screws, 

 K K, of which there are two pairs, — 

 one at each end of the machine (as shown 

 in Fig. 18). 



The construction , of the armature is 

 very interesting and ingenious. Each of 

 the induction coils shown at H (Figs. 19, 

 20, and 21) is composed, first, of a flat 

 spool or bobbin of the form marked 7i, and 

 then is wound in a lathe with insulated 

 copper wire 1.9 mm. in diameter, and of 

 which the total weight in the whole machine 

 is from 120 to 130 pounds. The iron 

 cores of these coils are built up of eighty 

 thicknesses of soft sheet-iron one milli- 



of eight laminae of steel. The distance 

 apart of the two limbs of each magnet, as 

 well as the distance between the north 

 pole of one magnet and the south pole of 

 the nest, is precisely equal to the distance 

 apart, or pitch around the armature, of 

 the pole-pieces and the coils. The details 

 of the magnets, and their method of adjust- 

 ment and attachment, are shown in Figs. 

 22 and 23. Each magnet is built up of 

 eight laminae of steel, each ten mm. in 

 thickness, and are held together tightly b3' 

 the bolts and nuts, cd, the whole being 

 attached to the brass frames, F, which are 

 fixed to the framing of the machine in 

 radial slides, by which the distance from 

 the armature ring can be adjusted with 



great accuracy. The total weight of the forty 

 magnets (see Fig. 16) is about one ton. 



The currents from the five armatures are 



metre in thickness, and stamped out by a 

 machine. The coils are wound, and attached 

 to the armature wheel by a set of bolts marked 

 e, which pass through the projecting lugs, g, of 

 the wheel, and through the cylindrical hole 

 formed by the semi-cylindrical grooves in the 

 ends of the iron core-pieces when abutting the 

 one against the other. 



The coupling-up of the armature coils is one 

 of the most ingenious features of the machine ; 

 for, as the magnets are arranged around the 

 armature in such a way that, in the rotation 

 of the coils, alternate poles are presented to 

 any one bobbin, it follows, that if the bobbins 

 were numbered 1, 2, 3, 4, etc., up to 16, the 

 currents induced in all the even-numbered bob- 

 bins would be in one direction, and in all the 



