26 REPORT — 1859. 



given out in the melting by pressure of the ice at the points of contact, where, from 

 the first two causes named above, the two slabs are urged against one another. 



The freezing of ice to flannel, or to a worsted glove on a warm hand, was, in his 

 opinion, to be attributed partly to capillary attraction acting in similar ways to those 

 just stated ; but he considered that, in many of the observed cases of this pheno- 

 menon, there are also direct pressures from the hand, or from the weight of the ice, 

 or from other like causes, which must be supposed to increase the rapidity of the 

 moulding of the ice to the fibres of the wool. 



On Electrical " Frequency." By Professor W. Thomson, LL.D., F.R.S. 



Beccaria found that a conductor insulated in the open air becomes charged some- 

 times with greater and sometimes with less rapidity, and he gave the name of "fre- 

 quency" to express the atmospheric quality on which the rapidity of charging de- 

 pends. It might seem natural to attribute this quality to electrification of the air 

 itself round the conductor or to electrified particles in the air impinging upon it; but 

 the author gave reasons for believing that the observed effects are entirely due to 

 particles flying away from the surface of the conductor, in consequence of the impact 

 of non-electrified particles against it. He had shown in a previous communication 

 that when no electricity of separation (or, as it is more generally called, " frictional 

 electricity," or "contact electricity") is called into play, the tendency of particles 

 continually flying off from a conductor is to destroy all electrification at the part of 

 its surface from which they break away. Hence a conductor insulated in the open 

 air, and exposed to mist or rain, with wind, will tend rapidly to the same electric 

 potential as that of the air, beside that part of its surface from which there is the 

 most frequent dropping, or flying away, of aqueous particles. The rapid charging 

 indicated by the electrometer under cover, after putting it for an instant in connexion 

 with the earth, is therefore, in reality, due to a rapid discharging of the exposed 

 parts of the conductor. The author had been led to these views by remarking the 

 extreme rapidity with which an electrometer, connected by a fine wire with a con- 

 ductor insulated above the roof of his temporary electric observatory in the island of 

 Arran, became charged, reaching its full indication in a few seconds, and sometimes 

 in a fraction of a second, after being touched by the hand, during a gale of wind and 

 rain. The conductor, a vertical cylinder about 10 inches long and 4 inches diameter, 

 with its upper end flat and corner slightly rounded off, stood only 8 feet above the 

 roof, or, in all, 20 feet above the ground, and was nearly surrounded by buildings 

 rising to a higher level. Even with so moderate an exposure as this, sparks were 

 frequently produced between an insulated and an uninsulated piece of metal, which 

 may have been about ^Vth of an inch apart, within the electrometer, and more than 

 once a continuous line of fire was observed in the instrument during nearly a minute 

 at a time, while rain was falling in torrents outside. 



Remarks on the Discharge of a Coiled Electric Cable. 

 By Professor W. Thomson, LL.D., F.R.S. 



Mr. Jenkin had communicated to the author during last February, March, and 

 April a number of experimental results regarding. currents through several different 

 electric cables coiled in the factory of Messrs. R. S. Newall and Co., at Birkenhead. 

 Among these results were some in which a key connected with one end of a cable, of 

 which the other end was kept connected with the earth, was removed from a battery 

 by which a current had been kept flowing through the cable and instantly pressed to 

 contact with one end of the coil of a tangent galvanometer, of which the other 

 end was kept connected with the earth. The author remarked that the deflections 

 recorded in these experiments were in the contrary direction to that which the 

 true discharge of the cable would give, and at his request Mr. Jenkin repeated 

 the experiments, watching carefully for indications of reverse currents to those 

 which had been previously noted. It was thus found that the first effect of pressing 

 down the key was to give the galvanometer a deflection in the direction correspond- 

 ing to the true discharged current, and that this was quickly followed by a reverse 

 deflection generally greater in degree, which latter deflection corresponded to a cur- 

 rent in the same direction as that of the original flow through the cable. Professor 

 Thomson explained this second current, or false discharge, as it has since been some- 



