426 Dr. Prours Reply to Dr. Yelhfy. [June, 



is, therefore, evident that rhodium may be rolled and made into 

 foil like platinum. But there is one curious circumstance which 

 will render it always brittle. If a quantity of the soda-muriate 

 be mixed with the black oxide, a regulus may be revived ; but 

 no degree of heat, nor any repetition of fusion, will render it 

 malleable. A portion of it will then always be converted into 

 glass, and it will exhibit a granular texture, depriving it of mal- 

 ieabihty. Nor is the soda-muriate itself so likely to be revived 

 in a malleable state as the black oxide of the metal, which never 

 fails. 



10. The hard carbonate of magnesia from the East Indies, 

 described by Dr. Henri/, in a late number of the Annals of Phi- 

 tosophy, fused before the gas blowpipe into a white enamel, com- 

 municates a purple colour to the flame. 



11 . A remarkable difference may be observed in the fusion of 

 the several crystallized and amorphous varieties of the phosphates 

 of lime. Some, like the white opaque apatite, from Devonshire^ 

 fusing into a jet-black gloss which is magnetic; others, as the 

 conchoidal apatite of Modum, in Norway, and the earthy apatite 

 of Estremadoura, fusing into greenish and limpid glasses, which 

 have no magnetic properties. 



To conclude all these observations upon the gas blowpipe, it 

 will be useful to some of your readers to be informed of the best 

 method of preserving the bladders employed for containing the 

 gaseous mixture ; because it is difficult to meet with very large 

 bladders, and they are soon rendered unfit for use without the 

 following precaution. Let them be kept carefully rubbed over 

 with oil, and distended with common air, when not wanted for 

 Experiments. By attending to this mode of preserving them, 

 we have found that the same bladder may be made to last in 

 constant use for the gas blowpipe, upwards of two years, without 

 becoming porous, which so frequently happens where the oil has 

 not been apphed, in consequence of the attacks of insects. 



Edward Daniel Clarke. 



Article IV. 



Reply to Dr. Yelloly^s RemarJcs on the Estimate of Mortality 

 from the Operation oj Lithotomy. By W. Prout, MD. FRS. 



(To the Editor of the Annals of Philosophy.) 



DEAR SIR, May %\82\. 



In reply to Dr. Yelloly's remarks on my estimate of morta- 

 lity from the operation of lithotomy in your last number, 1 beg 

 leave to observe that the adoption of the ratio alluded to is not 

 the result of inadvertency, but dcbi|^n.. My object is to give a 

 3 



