50 
been of very small dimensions, but in 1849 Nollet began the construction 
of an alternating machine on a larger scale, but died before it was com- 
pleted. Machines of Nollet’s type were afterward made by Holmes and 
by the Compagnie d’Alliance of Paris, the latter being called the Alliance 
machine. The machines were used for light-house purposes. Holmes’s 
earlier machines were continuous current, but later he left out the com- 
mutator and still later again introduced it on part of the coils for the pur- 
pose of obtaining current to excite his field magnets. This latter plan 
was introduced after the self-exciting principle had been introduced by 
Siemens and by Wheatstone. A remarkable machine, historically, was 
patented in 1848 by Hjorth. In this machine a combination of the per- 
manent and electro-magnet was used—the first to give magnetism enough 
to produce a current with which to excite the other. A similar idea was 
developed fifteen years later by Wilde with this difference, that the per- 
manent magnet part was a separate machine. The idea of using part of 
the current from the armature to excite or partially excite the field mag- 
nets was at this time in the minds of a number of workers, and some 
remarkable machines were patented by the brothers Varley, one of which 
containing both a shunt and a series winding has been held by some to an-- 
ticipate the compound winding now in use. In 1867 it seems to have 
occurred independently to Wheatstone and to Werner Siemens that the 
permanent magnet part of the Hjorth and Wilde machines might be dis- 
pensed with, the residual magnetism being used to start the action. Sie- 
mens gave the name dynamo-electric machine to this type, and it has 
stuck. In order to diminish the fluctuations in the strength of the cur- 
rent during one revolution of the armature, Pacinotti devised his multi- 
grooved armature machine in 1864. This machine did not receive the no- 
tice it deserved for a number of years, and in the meantime Gramme 
produced his smooth-ring armature in 1870. Gramme’s machine was soon 
recognized as being of great merit and its gradual introduction gave rise 
to increased activity. In 1873 the Hefner Alteneck improvements on the 
Siemens armature were introduced, and in the remaining 70’s quite a 
number of forms of dynamos were invented, the Lontin type, introduced 
in 1875, with improvement in subsequent years, being one of the best. 
The early SO’s saw tremendous activity. The patent offices in Europe 
and America were flooded with inventions of various types of dynamos 
and motors, of lamps for electric lighting, etc. It is curious how few of 
these machines have stood the test of time and how well the old types of 
