SCIENTIFIC SUMMAEY. 
397 
this phenomenon occurs in any part of the country, intelligence is immediately 
forwarded to the Admiral, who stated that he has found from experience 
that such disturbance of the electric wires is invariably followed by serious 
atmospheric changes, exhibited in the production of violent storms. The 
Admiral concludes that the atmospheric alteration is the effect of the electric 
change ; and the latter he conceives to be also productive of the abnormal 
action of the wires. Professor Tyndall, who was asked for his opinion upon 
the matter, considered that the facts were not yet sufficiently clear to warrant 
an expression of decided views. So the matter rests for the present. 
Standard of Electrical Resistance. — In reference to this subject, we have 
received a communication, which we subjoin for the benefit of those of our 
readers interested in electrical science ; — 
“ 6, Duke Street, Adelphi, London, W.C. 
“ Sir, — I have the honour to inform you that copies of the standard of 
electrical resistance chosen by the Committee on Electrical Standards, ap- 
pointed by the British Association in 1861, can now be procured by applica- 
tion to me, as Secretary to the Committee. 
“ The standard is a close approximation to 10,000,000 metre-seconds in 
Weber’s absolute electro-magnetic system, determined according to new and 
careful experiments made by different members of the Committee; and the 
copies are constructed of an alloy of platinum and silver, ii\ a form chosen as 
well adapted for exact measurement. 
“ The want of a generally recognized standard of electrical resistance has 
been universally felt, and led to the appointment of the Committee. They 
now desire me to express a hope that the motives which have led to their 
present choice, and which are fully explained in the several reports published 
by them, will induce you to assist in procuring the general adoption of the 
new standard. 
“ I remain. Sir, your obedient Servant, 
“ Fleeming Jenkin.” 
Electro-Chemical Fro])erties of Hydrogen. — A valuable article, showing the 
metallic properties of hydrogen, appears in Les Mondes, from the pen of M. 
Crova. The writer states in this that a metallic plate covered with hydrogen 
proceeding from the decomposition of an electrolyte, possesses an electro- 
motive force, varying with the intensity of the current ; that is to say, with 
the amount of gas disengaged in a given time at the surface of this plate, 
and which may be calculated exactly by meaus of a logarithmic formula. 
When mercury, containing a small but variable quantity of oxidizable metal, 
is employed as the negative metal of a pile, the electro-motive force dimi- 
nishes rapidly with the quantity of oxidizable metal contained in the amalgam, 
provided the quantity is very small. The hydrogen disengaged at the surface 
of a metallic plate is always more or less in a condition similar to that of an 
oxidizable metal contained in minimum proportion in an amalgam. Mercury 
which has served as a negative electrode in the decomposition of water has 
the property of disengaging, when heated, bubbles of hydrogen ; and when 
substituted for the zinc of a pile, it exhibits all the behaviour of an oxidizable 
metal, in which the proportion of this metal would be very small. Very pure 
mercury, through which a current of ordinary oxygen has passed, does not differ 
