1BI».] Scientific Lifelligence. 4G5 



greater, and that it goes much deeper, tlian has been hitherto sus- 

 pected. 



III. Arragonile. 



It may be worth while to state, that Stromeyer's discovery of the 

 presence of strontian in arragonite has been confirnied more than 

 six months ago at Paris by the experiments of Vogel, Laugier, and 

 Vauquelin, all of whom succeeded in obtaining crystals of nitrate 

 of strontian from arragonite. 



IV. JVhelhcr Cast-Lon expa?ids on congealins. 



In answer to the queries and doubts of my Correspondent N. N. 

 on this subject, I have to observe that Reaumur made a set of expe- 

 riments on the melted metals, and found that three of them expand 

 in the act of congealing; namely, cast-iron, bismuth, ar-d anti- 

 mony ; while all the rest contract. If you throw a piece (of toler- 

 able size) of gold or silver into these metals in fusion, it immeHi-itely 

 sinks to the bottom ; but a piece of iron will swim on the su:;a':e 

 of the melted mass. When melted iron congeals, the suiface is 

 not concave, as it would be if it contracted, but convex. The 

 allowance alluded to by N. N. for the shrinkage is in consequence 

 of the diminution of bulk before congealing, partly from couirac- 

 tion, and partly from leakage. If the iron had congealed before 

 the addition was made, it would be in vain to make it, as the addi- 

 tion would not unite with the old portion. 



V. On the Production of Complimentary Colours hj the successive. 

 Reflection of Polarized Light from Cold aiid Silvei: 



Dr. Brewster has discovered that if a pencil of polarized light 

 undergoes more than two reflections betvveen two polished plates, 

 cither of gold or silver, it consists of two portions, A and B, of 

 coloured light, the colours being complimentary to each other. The 

 portion A is polarized in the plane of reflection, and B in a plane 

 perpendicular to it. The colours of A and B vary after every two 

 reflections. The 2d and .3d, the «tli and 7th, the J 0th and 1 1th, 

 &c. reflected images are line, or composed of the most refrangible 

 rays ; while the 4ih and 5th, the Sth and 9tli, the 12th and i:5th, 

 &c. are redy or com|)osed of the least refrangible rays. The angle 

 of incidence upon the plates should be between 80° and .90°, and 

 the plane of reflection inclined 45° to the plane of the primitive 

 polarization. In order to perceive the colours, the reflected pencil 

 must be analyzed by a pri^im of Iceland spar. This singular pro- 

 perty is not posse'-sed by mercury, lead, steel, nor any other metal 

 which has beeii tried ; but all these metals possess another property 

 different from that of the gold and silver. 'I'besc experiments have 

 been repealed and verified by M. Biot, of the Institute of France. 



VI. O71 the MultifAivation of Images, aiul the Colours tchich 

 uccovipanij them, in some S/Jtcimcns of Iceland Spar. 



Profetisor Uobison, Martin, Brougham, and Malus, have success- 

 VoL. V. N* VI. 2 G 



