TRANSLATOR'S APPENDICES. 315 



WORK. 

 I kilogrammetre ~ T^foot-lbs. 



THERMOMETRIC SCALES. 



To convert centigrade degrees into Fahrenheit degrees 

 multiply by f or r8, and add 32 to the result. 



MONEY. 



i franc = 100 centimes 9*6 pence. 

 25 francs = i sterling. 



TRANSLATOR'S APPENDIX. No. 2. 



RECENT INVENTIONS. 



Since the publication of the original edition of this work, 

 the inventors of electrical apparatus have not been idle. 

 Patents without end have been, and continue to be, granted 

 almost daily for alleged improvements in current generators, 

 and for new forms of electric lamps. But none of these in- 

 volves any principle which has not been already illustrated 

 in the course of this work, nor does it yet appear that any- 

 one is destined to supersede such forms of apparatus as are 

 described in the text. Nevertheless, there are some quite 

 recent developments of certain forms of apparatus that 

 greatly affect the problem of electric lighting, and these may 

 here be very briefly described. 



Incandescent Lamps. Incandescent lamps of ex- 

 tremely simple construction have been lately brought out by 

 several inventors. These are all identical in principle, con- 

 sisting of a slender filament of carbon enclosed in a vacuous 

 vessel. They differ in such particulars as the dimensions of 

 the carbon filament, the material from which it is prepared, 

 the method of attaching its extremities to the current con- 



