172 AXXUAL OF SCIENTIFIC DISCOVERY. 



under his directions, illustrating the various stages in their manufac- 

 ture. In the case of cast iron, the photographs show the graphite 

 and several different compounds of iron carbon, as well as pure iron. 

 In wrought iron, the character of the crystals and the arrangement of 

 the slag are well seen, and the change in the constituents and in the 

 structure, which occurs when it is converted into steel, is very strik- 

 ing. Other photographs show the change in structure produced by 

 melting and hammering steel. Some meteoric irons have a structure 

 very different from that of any of these artificial irons, as shown by 

 another photograph. On the whole, then, when such sections are thus 

 examined, we may see most clearly the cause of those peculiarities in 

 physical structure which give rise to the different kinds of fracture 

 characteristic of different sorts of iron and steel, and which are so inti- 

 mately connected with those properties which make each variety more 

 or less suitable for special purposes. 



SCULPTURE BY COLORED LIGHT. 



A special attraction of a recent evening assembly at the Duchess 

 of ^Wellington's in London, was a peculiarly novel alfresco exhibition, 

 consisting of the lighting-up under various effects of color of a num- 

 ber of choice works of sculpture arranged in the garden at the rear of 

 the mansion. These works included copies of Gibson^ " Venus," 

 Thorwaldsen's ideal rendering of the same goddess, Powers's "Greek 

 Slave," and others. The illumination of these beautiful works of art, 

 including the foliage of the trees and shrubs amid which they were 

 placed, was under the superintendence of Professor Pepper, who ap- 

 propriated to this purpose large voltaic batteries arranged on Grove's 

 principle, which were connected with lamps and parabolic reflectors, 

 constructed by M. Serrin of Paris. The colors applied to this object 

 were vivid shades of red, amber, blue, green, and white, the ever- 

 changing and floating beams of colored light on the various groups 

 producing a most charming effect. London Times. 



ARTIFICIAL RAINBOW. 



The Cosmos speaks highly of J. Diiboscq's contrivance for imitating 

 a rainbow in a French theatre. He employs an electric light made by 

 100 Bunsen elements. Its rays are transmitted in a parallel direction 

 by means of a lens through a slot in the form of an arc, to a double 

 convex lens of very short focus, from which the rays pass to a prism, 

 and emerge with sufficient divergence to make an effective rainbow, 

 during the ordinary illumination of the stage, on a screen 18 or 20 feet 

 distant. 



THE COLOR OF TROUT. 



Mr. St. John adverts to the wonderful capability which trout pos- 

 sess of adapting their color to the color of the water in which they are 

 placed. "Put a living black burn trout," he says, " into a white 

 basin of water, and it becomes, within half an hour, of a light color. 

 Keep the fish living in a white, jar for some days and it becomes ab- 

 solutely white, but put it into a dark-colored or black vessel, and al- 

 though on first being placed there the white-colored fish shows most* 

 conspicuously on the black ground, in a quarter of an hour it becomes 

 as dark-colored as the bottom of the jar, and consequently difficult to 

 be seen." 



