1818.] Scientific Intelligence. 455 



a view to discover if I might not have been deceived. On reco- 

 vering the spider I found it was of the species " Aranea Scenica." 

 It had assumed a perfectly black colour; was, on being ap- 

 proached or disturbed, remarkably brisk in his motions ; but at 

 other times would drag his legs after him in a peculiarly sluggish 

 manner. Having cleaned the box, I deposited the insect in it 

 with a lump of nearly two ounces of sulphate of zinc. In about 

 10 weeks he had pierced this also, and as usual had produced a 

 considerable portion of the powder. I then deposited other 

 metallic salts, ,as sulphates of iron, lead, and copper, muriates 

 of lead and mercury, and nitrates of copper and silver, with the 

 sulphate of zinc in the box ; but the spider did not leave the 

 latter, nor did he touch either of the other salts, though I removed 

 the sulphate of zinc for a time from the box. Being thus satis- 

 fied of the fact, I endeavoured to ascertain if the salt had 

 undergone any chemical change in passing through the spider. 

 I caused him to fast two days, then deposited him in a clean 

 box with 200 gr. of sulphate of zinc ; and when I perceived he 

 had eaten nearly half of it, I carefully weighed the remainder 

 with the powdery substance ; it weighed 170 gr. : here was a 

 loss of near 30 per cent. This, however, might be in part water. 

 I, therefore, collected 60 gr. of the powder, on which I poured 

 six ounces of boiling water. A considerable part remained 

 undissolved, though frequently agitated, during two days. Ten 

 drops of sulphuric acid were then added, and the whole was dis- 

 solved. It seems probable, therefore, that the sulphate of zinc 

 had been deprived of part of its acid in passing through the spider. 

 The insect at this time seems perfectly healthy, having eaten 

 nearly four ounces of the salt in about six months. X. 



VI. Query respecting the Decay of Iron Rails 



(To Dr. Thomson.) 

 SIR, London, Sep!. 42, 1818. 



The decay of iron bars and rails at their bases, whether let 

 into stone or cast-iron, cannot have escaped the attention of a 

 numerous class of your readers as well as yourself. May I, 

 therefore, beg the favour of you, or such of your readers as have 

 considered the subject and had experience of the evil, whether 

 any remedy or palliation has been yet discovered, and what such 

 remedy or palliative is ? It has been suggested to me, that gray 

 paper wrapped round the end of the bar will have some effect. 

 If so, powdered gray paper might be employed in the same way 

 as lead, to fill up the holes into which the bars are inserted. 

 Lead has no effect, nor wood, as far as I have observed. Query 

 putty, roman cement, tallow, and manganese, &c. ? 



Your constant reader, W. D. S. 



VII. Query respecting Wronski. 



London, jiug. 17 , 1818. 



Allow me to inquire, through the medium of the Annals, whe- 

 ther any thing, and what, has been published in this country on 



