218 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



but the hydrogen does not again become occluded in the 

 iron plate. Hydrogenized iron can be easily pulverized, 

 but after it has been heated it retains a certain ductility. 

 Hydrogen, in associating itself with the iron, communicates 

 to it considerable magnetic force, so that the presence of 

 hydrogen in iron modifies greatly the magnetic properties 

 of this metal. 



MICROSCOPIC EXAMINATIONS OF THE PROCESS OF CRYSTAL- 

 LIZATION. 



Professor Frazer, Jr., exhibited to the Academy of Nat- 

 ural Sciences of Philadelphia a combination of the polar- 

 izer, vertical lantern, and microscope, by means of which 

 the manner in which different salts crystallize out of their 

 solutions, together with the manner in which they affect 

 polarized light, can be explained and illustrated. The light 

 from a lime lantern is passed through a rubber tube polar- 

 izer, then upward through the vertical lantern and a two- 

 inch lens microscope, when it is again reflected horizontally 

 on the screen. He explains that while this method has the 

 advantage of so magnifying the crystals produced from 

 small quantities of solutions that their structure can be mi- 

 nutely observed, as well as the sudden molecular change 

 which causes the polarizing effect, it is open to* the objec- 

 tion of a very large loss of light, first by the polarizer, and 

 again by the microscope. Apart of this difficulty, however, 

 can be obviated by the use of the parabolic reflector. Proc. 

 Acad, Nat. Sci., Phil, 1875, 16. 



A BRITTLE ALLOY OF IRON AND HYDROGEN. 



Mr. Johnson communicates to Nature some important ob- 

 servations in reference to the action of hydrogen on iron 

 and steel. Experiments made by him have shown that any 

 acid which gives off hydrogen, when it is allowed to act 

 upon iron or steel, produces the same effect, viz., of depriv- 

 ing the metal of its original toughness, and gives it the 

 property of frothing when moistened with saliva. The gas 

 coming oft' the surface of the iron, if cold, is shown to be 

 hydrogen; and it seems probable that the brittleness of the 

 metal is due to the occlusion of hydrogen within the iron. 

 The simplest way of charging a piece of iron with hydrogen 





