236 Progress of Invention. 



with, a small helix of wire, which, however, offers so little resistance 

 to the ordinary galvanic current, on account of its low intensity, 

 as to divert but a very small amount of it from the helix belonging 

 to the electro-magnet. Were the wire of the resistance coil, thus 

 introduced, of any considerable length, the effect produced upon it 

 by induction would be very mischievous. But its resisting power 

 is derived, not from its length, but from the material of which it is 

 formed. This being a very thin wire of iron, or, better still, of 

 maillechort, an alloy of zinc and cobalt. A helix containing only 

 one metre of the latter will produce as much resistance as many 

 kilometres of telegraphic -wire, and thus the interposed helix may, 

 for the largest electro-magnet, be extremely minute. 



Phosphorus a Metal : the so-called Amorphous Phosphorus 

 capable op Crtstallization. — Certain properties of phosphorus lead 

 to the conclusion that it is a metal very similar to the other metals 

 arsenic, antimony, and bismuth, belonging to the group in which 

 it is found : but the supposition is strongly confirmed by recent ex- 

 periments, in which the property possessed by lead of dissolving 

 phosphorus is applied to the production of phosphorus in the crys- 

 talline form. The phosphorus is put, along with the lead, into a 

 thick tube of hard glass, the interior of which is next exhausted of 

 air, and hermetically sealed. The glass tube is then placed in an 

 iron tube, capable of being closed at the ends ; and the space be- 

 tween the tubes is filled with magnesia, after which the apparatus is 

 kept at a high temperature for eight or ten hours. On cooling, the 

 surface of the lead is found covered with crystals of phosphorus, 

 which, like those of arsenic, antimony, and bismuth, are rhombo- 

 hedric. They have a metallic appearance, and are black by reflected, 

 but red by transmitted light. Their specific gravity is greater than 

 that of the ordinary and even of the amorphous phosphorus, being 

 2-34, while that of the others is 1-82 and 2T4. The volatilities of 

 these three different kinds of phosphorus differ in a similar way. 



The so-called amorphous or red phosphorus can now be easily 

 crystallized. For this purpose, M. Blondlot, who discovered the 

 fact, draws out the neck of a matrass in a lamp until it is about 

 the size of a quill. He then fuses phosphorus under water in glass 

 tubes capable of passing through the contracted neck, and intro- 

 duces two grammes of the cylinder thus obtained into the matrass, 

 having previously wiped them with filtering paper : after which he 

 hermetically seals its neck, keeping it during the process wrapped 

 in a moist cloth to prevent the phosphorus from igniting. It will, 

 however, emit light while combining with oxygen, and this com- 

 bination will be complete in twenty-four hours, after which its 

 temperature is to be raised to that of fusion, solar light being 

 excluded by covering the matrass with a truncated cone formed of 

 cardboard. After a few hours, brilliant points will make their ap- 

 pearance in the upper part of the matrass, and after two or three 

 days crystalline arborisations will have covered its whole surface. 

 The crystals thus formed are cubes, sometimes octohedrons, and 

 sometimes in the form of long projecting needles. As long as they 

 are kept from light they are colourless, but even diffused daylight 



