THE TINFOIL GRATING DETECTOR FOR ELECTRIC WAVES. H% 



distance into the gap, a 6, and forms the slope men- 

 tioned above. Along this slope the tinfoil presents v ^' 

 many folds or wrinkles, which seems to show that 

 the tinfoil strip was somewhat stretched along its edge / ff 

 by the act of cutting it. Non-sensitive gratings, 

 showed none of these characteristic appearances, but had the gap 

 between the strips much wider, with no decided slope and no 

 appreciable folds along the edges of the strips. Hence for a grating 

 to be sensitive, it appears to be necessary that the gaps should be 

 narrow and their margins sloped and in folds. 



§ 5. Although I have been unable to see clearly the interior 

 of a gap, yet it is quite reasonable to assume that in sensitive gratings 

 there will be numbers of leaflets along the margins of adjacent tinfoil 

 strips ; and the existence of such leaflets once admitted the explana- 

 tion of the action of the gratings becomes clear. For, in a properly 

 constructed grating some of the leaflets may easily come in contact 

 with one another under the action of the electric waves, because of the 

 extremely small distance between any two opposite leaflets in the 

 narrow gap. Then, too, it seems to me that these leaflets must be of 

 various dimensions and, accordingly, some of them will be extremely 

 sensitive, others less so but still highly sensitive, others again only 

 moderately so. This being the case, the amount of change in the 

 resistance of the grating must depend upon the intensity of energy 

 of the impinging electric oscillations, for, when it is not great 

 enough, only the most sensitive leaflets will come into play, but 

 when it is sufficiently great all the effective leaflets will be brought 

 into action. All the experiments I have yet made are in agreement 

 with this representation of the matter. 



§ (5. A grating, Avell prepared so as to fulfil the conditions 

 mentioned above, proves to be an extremely sensitive detector for 



