286 On the Reflection of Cold. 



ship, in the year 1798, first brought this plant from Brazil 

 to the Isle ot France, ;is a panacea. It was immediately 

 used against all kinds of diseases, and he extols its wonder- 

 ful effects, that it removes consunjption of the lungs, and 

 that it w?,p employed in the Isle of France as the surest 

 means against the bite of serpents; yet it is known that no 

 serpents are to be found in either of the Mascarhenas. 

 " All errors," says Bory, " continue only for a time. This 

 quackery also has ceased; the avapana is as little a panacea 

 as the German ' Forget mc not.' Bory himself took the 

 infusion of thirty leaves, for a catarrh, without the least 

 effect. People in the Isle de France remember the ayapana 

 only to laugh at the follies related of this plant, and the 

 charlatan who introduced it is forgotten." 



ON A LETTER IN OUU LAST NUMBER. 

 SIR, 



In your last number, page 1 71, I used too strong a 

 word, when I said that the Academy del Cimento had 

 successj'td/i/ repeated Bapthta Porta's experiment on the 

 reflection of cold. The fact is, that, not having had the 

 Essays of that bodv at hand, I quoted from memory. But, 

 as I have since met with the book, perhaps the best way 

 of correcting the mistake, will be to subjoin their own 

 brief account of the experiment. 



" We were willing, say they, to try if a concave glass 

 set before a mass of 600lb. of ice made any sensible reper- 

 cussion of cold, upon a very nice thermometer of 400 

 deorces, placed in its focus. The truth is, it immediately 

 bcaan to subside ; but, by reason of the nearness of the 

 ict^, 'twas doubtful whether the direct or reflected rays of 

 cold were more efficacious. Upon this account, we thought 

 of covering the glass, and (whatever be the cause) the 

 spirit ot wine did indeed presently begin to rise. For all 

 this, we dare not be positive, but there might be some 

 other cause thereof, besides the want of reflection from the 

 glass; since we were deficient in making all the trials ne- 

 cessary to clear the experiment." — See the 9th " Experi- 

 ment of Natural Freezing," at page 103, of the Essays of 

 Natural Experiments, made in the Academy del ChnentOf 

 published i.i 1 Gtw, and translated by Richard JValler, F.R.S. 

 London l6&4. Yours, &c. *D. 



INGENUITY OF THE SPIDER. 



T. A. Knight, Esq. of Herefordshire, has, in a treatise , 

 on the culture of the apple and pear, introduced the follow- 

 ing anecdote concerning this curious animal : — " I have 



frequently 



