EFFECTS OF HEAT ON FLUIDS. 419 



so as to make a completed circuit of the primary wire (a 

 condition which would have appeared a priori essential to 

 success), no effect was produced ; while if the circuit was in- 

 terrupted by keeping the contact-breaker open, sparks of 0*3 

 of an inch passed between the terminals of the secondary 

 coil of the Ruhmkorff, and vacuum-tubes were readily illumi- 

 nated. Here there was in effect no primary coil, no metallic 

 connexion for the primary current ; and yet a notable effect 

 was produced. 



I did not at the time publish this experiment farther than 

 by communicating it to a few friends, hoping to be able to 

 find a satisfactory explanation of it. All I have observed 

 since is that the effect is dependent upon the condenser, for 

 when that is removed no result is produced. 



It would appear, then, to depend on an electrical wave or 

 impulse, shot, so to speak, into the uncompleted primary coil, 

 similar to the wave which will deflect in succession magnetic 

 needles placed at different distances on a telegraphic cable, 

 without the current passing through the whole length of wire, 

 as shown in the experiments of Mr. Latimer Clark and others. 

 But why there should be no effect, or an inappreciable one, 

 when the primary circuit is completed, the current being alter- 

 nated by the rotation of the coils of the magneto-electric 

 machine, I cannot satisfactorily explain. 



ON SOME EFFECTS OF HEAT ON FLUIDS. 



Journal of the Chemical Society -, May 21, 1863. 



HAVING been honoured by an invitation from the Council of 

 the Chemical Society to give a lecture on one of the evening 

 meetings of the Society, it was not without hesitation that I 

 accepted the task. My professional occupation having of late 

 years so much prevented any continuous devotion of mind to 

 scientific investigation, it was only by reverting to researches 

 made several years ago that there was a chance of my com- 

 municating anything worthy the attention of the Society. I 



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