1867.] Physios, W 



remains uniform, however the heat from the source varies ; but if 

 the smallest variation takes place in one of the radiations, the 

 needle quits the zero point. The author has applied this apparatus 

 to the examination of the absorption of heat by transparent gases, 

 and finds that it gives very delicate and certain indications. 

 This may be the case, but we do not see that the arrangement 

 described by M. Desains is superior to Wheatstone's Bridge, 

 the construction of which is peculiarly simple and easy, whilst the 

 correct adjustment of a double wire differential galvanometer is a 

 most difficult and uncertain operation. 



The chemistry of the galvanic battery is a subject which would 

 seem to have become almost exhausted. M. Favre has, however, 

 contributed some important experiments, in which he has examined 

 the amount of heat set in motion during galvanic decompositions or 

 combinations. The conclusions at which he arrives are, that when 

 a body is decomposed by the battery, the constituent elements, in 

 separating, absorb a larger amount of heat than they disengage 

 again in combining under ordinary circumstances. Thus, in the 

 nascent state, bodies possess an excess of heat, which they give up 

 on becoming modified to the ordinary state. The author's experi- 

 ments reveal another fact, — that secondary actions take place in the 

 battery, accompanied by a disengagement of heat, which is not 

 turned to account in the current, and therefore he says that electro- 

 magnetic machines cannot dispose of all the heat set in action in 

 the battery. 



M. de Gernez has investigated the subject of the disengage- 

 ment of gases from their supersaturated solutions (of the soda- 

 water type) and has discovered the following facts: — 1st. Solid 

 bodies, from which the gaseous bubbles are disengaged, lose their 

 property after a certain time. 2nd. Prolonged soaking in water 

 also removes this action from them, 3rd. Heat has the same 

 action. 4th. Solid bodies, which have been in contact with air, 

 have no action on supersaturated gaseous solutions. 5th. Air and 

 gases provoke the disengagement of dissolved gas. 



Electricity. — Electricity, although the youngest of the 

 sciences, has already produced such marvellous results that some 

 knowledge of its principles must, in future, form part of a liberal 

 education. To impart this knowledge in a concise form has been 

 the aim of Doctor Noad in his ' Text Book of Electricity.'* Of 

 course, in a work of this sort, much originality is not expected, nor, 

 indeed, would it be considered so desirable as a judicious selection, 

 from acknowledged authorities, of those facts which form the 

 groundwork of the science, and the truth of which has been 



* « The Student's Text-Book of Electricity.' By Henry M. Noad, Ph.D., F.K.S., 

 F.C.S., &c. London : Lockwood & Co. 



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