PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 649 



6. As the expense of such an apparatus is $150 to $300, is one 

 objection ; a patent was taken out by Mr. Seely, of this city, to 

 substitute for the former apparatus, a common glass disk electric 

 machine, hermetically inclosed in a glass case, and kept perfectly 

 dry with chloride of calcium to secure it against the occasional 

 dampness of the atmosphere, which is the cause that common 

 glass electric machines do not work half the time. Similar ma- 

 chines have been made in Holland 20 years ago. One is now in 

 possession of the University of Groningen. 



7. Very recently a patent was taken out by Mr. Batchelder 

 for the connection of a vulcanized India rubber disk of 3-inch 

 diameter, with the chandelier in which it is hidden ; by turning a 

 knob at the lowest part of the chandelier it produces by friction 

 some electricity, which is conducted by isolated wires to the six 

 or eight burners of that chandelier, producing there little sparks 

 sufficient to light the gas. 



8. Still later a patent has been applied for, for a similar India 

 rubber disk, which, by turning, lights a small alcohol lamp, and 

 thus allows one to dispense with the use of matches. I must 

 here observe that India rubber and gutta percha are much less 

 apt than glass to condense moisture from the atmosphere on their 

 surface, and therefore electric machines made out of those sub- 

 stances are more certain in their effects than the glass machines, 

 and about as certain as the machine mentioned under No. 6, 

 above. 



9. As the large battery used in No. 3, above, for the heating 

 of the platina wire, may be considered an objection, I experi- 

 mented more than a year ago to effect the same with a magno- 

 electric apparatus, in which a soft iron core is unwound with a 

 coil and revolves in front of a bundle of seven powerful steel 

 magnets of horse-shoe form, of two feet length. As the quantity 

 of electricity produced in this way is sufficient to heat this pla- 

 tina wire, as all those know who are acquainted with this appa- 

 ratus, this heating being one of the common lecture room experi- 

 ments, nobody will doubt that I am able to light gas with it, and 

 every one else may. 



(Dr. Van der Weyde here tried the experiment of lighting the 

 gas by this process, and after a few attempts succeeded in doing 



60.) 



Also this arrangement has been applied to produce electric 

 currents for medical use. The slightest modification in it has 



