1823 J Scientific Intelligence. 75 



with the saline solution, the temperature of the vapour is the same as that 

 of the solution itself. We understand that Mr. F. has verified M. Gay- 

 Lussac's statement by experiment, and satisfied himself of its accuracy. 



II. Index to Kirby and Spences Entomology. 



(To the Editor of the Annals of Philosophy.) 



DEAR SIR, Dec. 22, 18S2. 



I beg to submit, through your journal, to the learned authors of the 

 Introduction to Entomology how important an addition to each of their 

 delightful volumes a pretty copious index would be ; and how imperfect 

 their work is without it. It is of course intended that the last volume 

 should comprise all that is necessary in this way; but this is not 

 enough, for during the many years that intervene between the appear- 

 ance of the first and the last volume, the entomological student is 

 deprived of all the advantages of reference, unless he make an index 

 for himself. All the leading facts of the two first volumes may be very 

 readily embraced in one index ; and I would suggest to Messrs. Kirby 

 and Spence, that it would be desirable to furnish this assistance to the 

 public without delay, as well as to provide every future volume with 

 an index for itself, with the exception of the last, which will necessa* 

 rily contain general references for the whole work. 



I remain, dear Sir, yours sincerely, 



NoRFOLCIENSIS. 



III. Separation of Plumbago from Cast-Iron. 



A curious paper on this subject has appeared in No. 14- of the Edin* 

 burgh Philosophical Journal ; the facts related in which we shall pro- 

 ceed to state, and afterwards to offer a few remarks on the theory 

 which has been deduced from them by the writer of the paper, Dr. Mac 

 Culloch. 



In the frequent examination of the metal of the iron guns delivered 

 by the contractors to the ordnance, by solution, according to Berg- 

 man's suggestion, Dr. M. found that the quantity of plumbago in the 

 metal bore no relation to its strength or goodness, but that the results 

 were sometimes curious, from the very variable quantity which differ- 

 ent specimens of the iron contained. The trials were far from confirm- 

 ing the opinion that the worst or weakest metal contained most plum- 

 bago; and on one occasion, an exceedingly tough specimen was found 

 to contain a most unusual proportion of this substance, and that in a 

 disengaged state, being visible on breaking the metal: which appeared 

 as if it had been rubbed with powdered black-lead, and left its trace on 

 paper. Where the plumbago was most abundant, the colour of the 

 fracture of the iron was most grey ; and Dr. M.'s trials go to prove, in 

 contradiction to the opinion of many iron-founders, that the greyest 

 metal is the toughest. The plumbago was always obtained in the state 

 of powder, and in very small proportion when compared to that 

 obtained from pig-iron. 



The same experiments were repeated on the pig-metal used for 

 shells, which is generally distinguished into three kinds; white, grey, 

 and black. All these afforded very large proportions of plumbago, but 

 various in different specimens; the black metal seemed to afford the 

 greatest quantity, but that which was most brilliant and silvery also 



