52 Dr. 0. Lodge on Electric Radiation. 



weight of the pitch ripped the zinc from its fastenings, and a 

 horrid collapse was the result. 



A couple more moulds were made of the same pattern, only 

 stronger, and a bed of sawdust and mould was made to 

 sustain the weight. A double partition of thin wood was 

 introduced across the middle of the mould, so as to enable 

 each lens to be split into two halves if it should happen to be 

 too immovable in one piece. 



After a time two satisfactory lenses were obtained, each 

 nearly a metre square. Nothing could be done with them 

 during term, because of want of space; but in the Easter 

 holidays I requested my demonstrator, Dr. Howard, to make 

 experiments in one of the College corridors. There exists a 

 large open room or iron shed, which I should have preferred 

 to use ; but unfortunately dry rot had set in in its flooring, 

 and it was in the hands of the carpenters all vacation. We 

 are therefore somewhat troubled by neighbouring walls and 

 by hotwater-piping. 



Under more favourable circumstances, the distance between 

 the lenses might no doubt have been much greater ; in fact, 

 no attempt was made to place the lenses far apart. They 

 were set up with their flat faces parallel at the opposite ends 

 of a table, about 6 feet apart, and not afterwards moved, 

 being, indeed, rather unwieldy ; the oscillator was placed in 

 the principal focus of one lens, viz. at a distance of from 41 

 to' 51 centim. from its curved surface. The focal length, 

 calculated on the assumption that jjl= 1*7, was 41 centim., but 

 experimentally 51 centim. seemed to do better. 



After the few experiments here recorded were done, one of 

 the lenses took advantage of Easter week to assert its essential 

 fluidity, and so much bulged and curved over as to be almost 

 unserviceable ; since then it has completed its ruin by 

 breaking its prop and tumbling over into fragments. The 

 other lens stands remarkably well, and seems as good as 

 ever. There is evidently an important difference in the 

 quality of the pitch, though it is not a difference recognized 

 by the invoice. On the whole I think paraffin would have 

 been the best substance to use. 



The particular form of receiver is a comparatively unim- 

 portant matter, but I prefer linear ones to circular or nearly 

 closed circuits as being more sensitive at great distances, 

 for much the same reason as has been stated for oscillators. 



Exact timing of the receiver is unessential. If resonance 

 occurred to any extent, so that the combined influences of a 

 large number of vibrations were really accumulated, the effects 

 might doubtless be great ; but hitherto I have seen no evi- 



