lxx GENERAL SUMMARY OF SCIENTIFIC AND 



Spottiswoode lias constructed a modified form of polari- 

 scope, which lias some decided advantages. It consists of a 

 Nicol's prism as the polarizer, and a double-image prism as 

 the analyzer, the latter being so cut as to show one image in 

 the centre of the field, the other being excentric. By rapid- 

 ly rotating the analyzer, the ring image remains by persist- 

 ence and displays the phenomena, usually successive, simul- 

 taneously. 



Becquerel, in a research upon magnetic rotatory polariza- 

 tion, has extended the list of substances possessing this prop- 

 erty, and has determined exactly the power of rotation for a 

 given thickness of plate and a given magnetic intensity. In 

 general, he finds that increase of magnetic rotatory power 

 follows increase of the refractory index. 



Bertin has given a notice on projecting polarization phe- 

 nomena with the apparatus of Duboscq, dividing these phe- 

 nomena into three classes those requiring (l) parallel, (2) 

 divergent, or (3) convergent light. 



Riche and Barely have reported upon the sources of illumi- 

 nation utilizable in photography, in which they give the re- 

 sults of their examination of eight different sources of light, 

 viz., the oxyhydrogen light, the Drummond or lime light, 

 zinc burning in oxygen, magnesium in air, a current of nitric- 

 oxide gas burning in a globe of carbon-disulphide vapor, a 

 jet of nitric oxide in a test-tube containing carbon-disulphide, 

 a jet of oxygen in the same, and a jet of oxygen in a test- 

 tube containing sulphur. The eight lights were photo- 

 graphically intense in the order above mentioned, the last 

 beinsr ei^ht times as strong as the first. 



Vogel has proposed a simple form of camera for spectrum 

 photography, which consists simply of a box, in one side of 

 which is fixed, by means of a cork, a pocket spectroscope. 

 With this instrument a picture of the solar spectrum from II 

 to D was taken on silver bromide mixed with naphthalin- 

 red in three minutes. 



MAGNETISM. 



In Magnetism, Rowland has described a simple method 

 of determining the distribution of magnetism on iron and 

 steel bars by means of a small coil of wire one quarter to 

 one half an inch in diameter, containing from ten to fifty 



