Intelligence and Miscellaneous Articles. 167 



of the sun's action on a photographic surface with that of flame, the 

 centre rays of the latter being also more intense in chemical action 

 than those at the circumference. 

 Parsonstown, July 1864. 



ON THE COLOURING-MATTER OF EMERALDS. 

 BY MM. WOHLER AND G. ROSE. 



Vauquelin, after having discovered oxide of chrome in the eme- 

 rald, attributed to this oxide the green colour of the stone. In 1858 

 M. Lewy published very interesting researches on the deposit, the 

 formation, and the composition of the emeralds of Muso in New 

 Granada. His conclusion is that the colour is due to an organic 

 substance, the existence of which he proved by very accurate expe- 

 riments. Thus he says that the green colour disappears when the 

 emeralds are heated to redness. As we were unable to verify this 

 assertion in the blowpipe experiments to which we subjected the 

 emerald, M.Rose and myself exposed a piece of Muso emerald, weigh- 

 ing 7 grammes and of a deep green colour, for an hour to the tem- 

 perature of melting copper. The colour did not disappear ; the spe- 

 cimen simply became opake. Yet it had lost 1*62 per cent, of its 

 weight, which agrees closely with the numbers given by M. Lewy. 

 On analysis the above specimen gave 1*186 per cent, of its weight 

 of oxide of chrome. M. Lewy thinks that such a small quantity of 

 oxide is insufficient to communicate so pronounced a tint to eme- 

 rald. 



To settle this question, we melted 7 grammes of colourless glass 

 with 13 milligrammes of oxide of chrome. We thus obtained a trans- 

 parent homogeneous glass of a green colour, identical with that of 

 the emerald analyzed. Hence it seemed proved that 13 parts of 

 oxide of chrome are sufficient to communicate a very deep green 

 colour to 7000 parts of a silicate, and we do not hesitate to assume 

 that the colour of emerald is due to oxide of chrome, without, how- 

 ever, contesting the existence of an organic substance in this mineral. 

 — Comptes Rendus, June 27, 1864. 



RESEARCHES ON THE RESPIRATION OF FLOWERS. 

 BY M. CAHOURS. 



The author gives the following summary of the results arrived at 

 in the course of his researches : — 



1. Every flower left in a confined space of normal atmospheric air 

 consumes oxygen and produces carbonic acid in variable proportions, 

 whether the flower has odour or not. 



2. The circumstances in which this takes place being the same, 

 the proportion of carbonic acid increases as the temperature rises. 



3. That generally for flowers gathered on the same plant, and 

 whose weights are virtually equal, the quantity of carbonic acid pro- 

 duced is somewhat more considerable when the apparatus in which 

 the experiment is made is exposed to light, than when placed in 



