ON THE INDUCTION-COIL. 



209 



tage gained from the condenser was much greater, and the utility of 

 the quicker break, with or without condenser, seemed to be nil. 



But, in spite of the failure of the qnick break, one or two observa- 

 tions présentée! themselves which seemed worthy of being followed up. 

 It was notieed that, with one Grove cell in the primary, the spark, 

 although very iuferior when no condenser at ail was employed, was 

 improved when the usual condenser (or large capacity) was replaced by 

 a single sheet of coated glass (Frankt/in's pane). And, what was per- 

 haps more instructive still, when the already weak priraary current was 

 further reduced by the insertion of one or two ohms extra résistance, 

 the spark-length (now very s m ail) was less with than without the usual 

 coil condenser. This observation was repeated, with like resuit, upon 

 another coil (by Apps) and its associated condenser. At any rate in the 

 case of very weak primary currents, the usual condenser did harm 

 rather than good. 



The view, suggested by the foregoing results, that while the ordinary 

 break was quick enough in the case of weak currents to allow a con- 

 denser to be dispensed with, the superior arcing power of strong cur- 

 rents demandée! a much more rapid break, encouragée! further efforts. 

 An attempt to secure suelelenness by forcibly breaking with a jerk a 

 length of rather thin copper wire, forming part of the primary circuit, 

 faileel entirely, as die! also, perhaps for want of sufficiently powerful 

 appliances, an attempt to blow up a portion of the primary circuit by 

 electric discharge. Another method, however, at once allowed an ad- 

 vauce to be securecl. Tins consistée! in cutting the primary circuit by a 

 pistol-bullet; and it was founel that this form of break without con- 

 denser was about as efficient as the usual platinum break with condenser, 

 although the primary current was increased to that suppliée! by three 

 or four Grove cells and the spark-length to 40 mm., that is, uneler 

 about the ordinary conelitions of working. 



A further improvement was effected by cutting away about half of 

 the bullet with the intention of raising its velocity. The following 

 results were recorded with an Apps 1 coil excitée! by three Grove cells. 

 The spark-gap being 50 mm., the usual platinum break and conelenser 

 were not able to senel a spark across. Even with the somewhat more 

 efficient break provided by a pot of mercury well drowned in oil and 

 condenser, only about one break in fifteen succeedeel. On the other 

 hand, of three bullets fired so as to eut the primary wire (no condenser) 



ARCHIVES NÉERLANDAISES, SERIE II. TOME VI. 14 



