Maecii 25, 1898.] 



SCIENdiJ. 



4o8 



Siemens that the permanent magnet part of 

 the Hjorth and Wilde machines might be 

 dispensed with, the resident magnetism 

 being used to start the action. Siemens 

 gave the name dynamo-electric machine to 

 this type and it has stuck. In order to 

 diminish the fluctuations in the strength 

 of the current during one revolution of the 

 armature Paciuotti devised his multi- 

 grooved armature in 1864. This machine 

 did not receive the notice it deserved 

 for a number of years, and in the 

 meantime Gramme produced his smooth 

 ring armature in 1870. Gramme's ma- 

 chine 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 dynamo were invented, the Loutin 

 type introduced in 1875 with improvement 

 in subsequent years being one of the best. 

 The early 80'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 and so forth. It is curious 

 how few of those machines have stood the 

 test of time and how well the old types of 

 Pacinotti, Gramme, Siemens-Alteneck and 

 Loutin in some one of their modifications 

 hold the field. Great progress has been 

 made in the last fifteen years. Machines 

 have assumed enormous proportions and 

 the number of bi-anches of industry to 

 which they have been applied is now very 

 large. Much has been learned during this 

 time, particularly with regard to alterna- 

 ting currents and their application to the 

 transmission of power, the introduction 

 of Multiphase systems being of considerable 

 importance in this connection. In the 

 direction of high potential and great fre- 

 quency the work of E. Thomson and Tesla 

 is of great intei-est. 



Of the application of electricity to the 

 production of light and heat little need be 

 said in this connection. The difficulties to 

 be overcome were largely mechanical, and 

 with the progress made we are all familiar. 



As regards primary batteries there has 

 been, of course, as we all know, consider- 

 able j)rogress since the time of Volta. The 

 number of forms brought into use has been 

 enormous and they have been important in 

 increasing our knowledge of the relative 

 electro-motive force of various combina- 

 tions and in their bearing on chemical 

 knowledge. It can hardly be said that an 

 ideal primary battery has yet been obtained, 

 when we look at the subject from a com- 

 mercial point of view. Although the sub- 

 ject is not very much to the front at pres- 

 ent, however, it is destined to come again, 

 and will, I have no doubt, be, in a compar- 

 atively short time, one of our leading in- 

 dustries. 



The work of Plante and of Faure and 

 others on secondary batteries has been of 

 great value commercially. They gave rise 

 to several chemical problems, but the main 

 difficulty here also has been of a mechanical 

 kind, and they have not added much to the 

 knowledge of electrical laws. 



The transformation of alternating cur- 

 rents from high to low potential and vice 

 versa, by means of what are commonly 

 called transformers, has shown another re- 

 markable development of Faraday's discov- 

 ery of induced currents. The application 

 of transformers has made it possible to dis- 

 tribute electrical energy over large areas in 

 a moderately economical manner, and inci- 

 dentally has led to considerable increase in 

 the knowledge of the magnetic properties of 

 iron. 



One of the most important of the applica- 

 tions of electricity is that of electrochemis- 

 try. The chemical action of the electric 

 spark was noticed by van Groest and Die- 

 man in 1739 in the decomposition of water. 



