318 Royal Society : — 



At the end of this time a cloudiness began to appear in the first 

 bulb of F, and after half an hour in the second bulb : finally, a 

 decided precipitate was obtained ; it was collected, washed, and on 

 analysis proved to be carbonate of calcium. The experiment was 

 repeated in a modified manner several times. It having been 

 found that a faint turbidity in the lime-water was sometimes ob- 

 tained before the addition of the beryl, it was traced to the pre- 

 sence of minute quantities of organic matter in the chromate and 

 sulphuric acid. To eliminate this source of error, the chromate 

 and acid were mixed at the commencement of the operation, and 

 the current of air was kept up until every trace of carbonic anhy- 

 dride was removed; at this point the beryl was added, and the 

 effect noted. The results, both with emeralds and the beryl A, how- 

 ever, were always precisely the same. 



The apparatus was then recharged ; and when half an hour's pas- 

 sage of the air produced no milkiness in F, 5 milligrammes of char- 

 coal were introduced into D ; in two minutes the first bulb, and in 

 four minutes all the bulbs were rendered milky. 



In another experiment, after the usual precautions, 5 milli- 

 grammes of graphite were acted on. In four minutes the first 

 bulb, and in eight minutes all three bulbs were rendered milky. 

 °" The above experiments show, therefore, that the beryl A con- 

 tains carbon, not in the state of a carbonate, but in a condition 

 which is more slowly attacked than either free charcoal or graphite ; 

 and it is, I think, probably in the form of diamond, as has been 

 shown to occur with the carbon contained in artificially crystallized 

 boron*. The power of free chromic acid to attack the diamond 

 with liberation of carbonic acid has been shown by the Messrs. 

 Rodgers t. 



The presence of carbon in beryls does not appear to be inva- 

 riable. After repeated experiments upon another large beryl from 

 Haddam County, North America, I was unable to satisfy myself 

 that it contained carbon. It is true that traces were found in the 

 experiment ; but they were so minute that they might have been 

 due to the difficulty of entirely excluding the presence of organic 

 dust during the necessary manipulations %. 



The next point I wished to ascertain was the relation borne by 

 the quantity of carbon in the beryl A to that in the emerald. 

 For this purpose I employed a similar apparatus to that used by 

 Dumas in his researches on the atomic weight of carbon previously 

 alluded to. The minute error due to the apparatus was carefully 

 determined by going through the whole process of heating the 

 combustion-tube to redness for the same time as in the analysis, the 

 current of oxygen passing through at the same speed, and finally 



* Wohler and Sainte-Claire Deville, Comptes Rendus, February 16, 1857. 



t R. E. Rodgers and W. B. Rodgers, Chem. Gaz. vol. vi. p. 356 (1848). 



\ Since the above paragraphs were written, an interesting paper has been pub- 

 lishedby Prof. Silliman, " On the Probable Existence of Microscopic Diamonds 

 with Zircons and Topaz in the Sands of Hydraulic Washings in California," 

 Chem. News, vol. xxvii. p. 212. 



