a fine Edge to Cutting- Instruments. 16 



sometimes led to suspect the operation of the bar to have been 

 something more than that of having worn away a minute por- 

 tion of the metal : but I am not disposed to offer any conjec- 

 tures respecting other effects which I may have conceived it to 

 produce. 



I have in many instances been able to give a very fine edge 

 to razors in possession of my friends, which I could not set 

 tolerably well by any of the ordinary means; and I have 

 found that those composed of different materials could be set 

 with equal facility, though the sensations they excited, when 

 used, appeared to me to be in many instances dissimilar. The 

 instruments upon which I have chiefly made experiments have 

 come from the manufactories of Mr. Pepys. Mr. Stoddart, 

 and Mr. Kingsbury. The material which appeared to me to 

 receive that which I shall call the most eager edge (and it was 

 very durable) was wootz, from the manufactory of Mr. Pepys; 

 and that which received the smoothest edge^ and which I 

 thought best calculated for surgical purposes, was the mixture 

 of rhodium and steel ; the powers of the pure steel of Mr. 

 Kingsbury appeared to be intermediate : and my experience 

 leads me to believe that, under different circumstances, each 

 of these materials might be used with some exclusive advan- 

 tages. 



ON THE PECULIAR HABITS OF CLEANLINESS IN SOME 



ANIMALS, AND PARTICULARLY THE GRUB OF 



THE GLOW-WORM. 



BY J. RENNIE, A.M., A.L.S. 



TN an excursion, for the purposes of natural history, to the 

 woods in the vicinity of Dartford, in Kent, the 14th of 

 last March, I found an insect, which I had not hitherto met 

 with, creeping upon the mossy trunk of an oak, which, besides, 

 was entwined with honeysuckle ; and, near the bottom, a fern 

 plant was rooted amongst the decaying bark. This insect 

 much resembled the female glow-worm in external appearance, 

 but it was considerably longer, and the colours different. Its 

 head, though small, was formed like those of the grubs of pre* 



