NATURAL PHILOSOPHY. 131 



ON FIXING MAGNETIC PHANTOMS. 



The name "phantom" was given by M. de Haltlatto the figures which are 

 obtained when iron-filings are thrown upon a sheet of paper or a pane of 

 glass placed over a magnet. This physicist fixed these images by producing 

 them upon a sheet of paper coated with starch or prepared with gelatine. 



This process certainly enables us to obtain the general form of the phan- 

 toms; but all physicists can see that it suppresses the details. I therefore pro- 

 pose another method, which is very simple, and succeeds perfectly. The 

 paper upon which the phantoms are to be fixed is " waxed" paper. A sheet 

 of this is placed over the poles of the magnet in question, and kept in a hori- 

 zontal position by means of a screen placed between the paper and the mag- 

 net. Then, proceeding in the usual manner, when the image is fully devel- 

 oped, a hot brick is held above it, or the warm lid of a crucible, which is 

 preferable, because it is lighter and easily managed with the tongs. They 

 must not touch the paper, but only be brought within the distance necessary 

 to fuse the wax. As soon as this happens, which is easily perceived by the 

 glistening appearance produced, the brick is withdrawn. Meanwhile the 

 current does not cease its activity, nor the filings lose their arrangement, in 

 which position the whole solidifies so well that the fixed image does not at 

 all differ from the phantom of the magnet in activity. Permanence is thus 

 given to the sort of molecular arrangement which the filings take when ex- 

 posed to magnetic influence. Instruction can hardly fail to be derived from 

 the use of these means, by aid of which it will be possible to study the fig- 

 ures more advantageously, which are, in some sense, the visible expression 

 of the force animating bodies endowed with polarity developed by mag- 

 netism. Professor J. Nickles, Silliman's Journal. 



ELECTRIC AND CALORIFIC CONDUCTION OF METALS. 



Messrs. Calvert and Johnson, after mimerous experiments, have arrived at 

 the conclusion that the electric and calorific conduction powers of conduct- 

 ing heat and electricity are proportional to each other in alloys as well as 

 in simple metals; and that these powers are exhibited by the alloys of cop- 

 per and zinc in a degree which differs little from that of zinc, whatever amount 

 of copper they may contain. The rapidity with which the conduction of 

 copper is reduced is very remarkable. Thus pure copper conducts electricity 

 with a facility represented by the figures 73.6, and heat with one represented 

 by 79.3; but when eight parts of copper are alloyed with one part of zinc, 

 the conductibility for electricity is reduced to 27.3, and for heat to 25.5; that 

 of zinc alone being for the former 28.1, and for the latter 27.3. The con- 

 ductibility of alloys of tin and bismuth is nearly the mean of that of the 

 component metals. 



ON THE CONSERVATION OF FORCE. 



Professor Faraday, in a recently published volume, entitled " Experimen- 

 tal Researches in Chemistry and Physics," adds to his former expressed 

 opinions, in relation to the conservation of force, 1 the following additional 

 remarks : 



1 See Annual of Scientific Discovery for 1858, pp. 177-189. 



