368 



Retrospective Criticism. 



" If the heat of the air be at any time excessive, it may be lessened.by openmg the end of the 

 tube at g, where it is usually kept closed. The hotbed, in which I have placed the above. 

 described kind of tubes, is composed almost wholly of leaves ; but the mass of these is great, and 



the temperature in consequence high. 1 immersed a deep pot into the leaves, and caused the 

 heated air of the tube k, to'ascend into it; having previously shortened the tube, and fitted it 

 accurately to the aperture of the pot, placing a thermometer, with some eggs of the common 

 domestic fowl within it, with the view of ascertaining whether these could be hatched by such 

 means. I have not yet seen the result; but the temperature of the; ascending current of air, 

 which arises into the pot, and, of course, into the frame, appears never to have varied during 

 fifteen days more than three degrees ; the lowest temperature being 101°, and the highest 104° ; 

 and it has, of course, been nicely adapted to both the purposes for which it was intended. 



" I have formerly ascertained, that the power of a current of heated air, when made to enter a 

 pit or chamber of any kind, was found greatly to exceed the calculation which I had previously 

 made ; and in the last winter, very contrary to my expectations, a very feeble current of air, the 

 temperature of which was below 50°, proved sufficient to preserve geraniums, which were placed 

 close to the glass, in the severest frost from receiving the slightest injury. 



" The operation of a hotbed, into which a pipe is introduced in the manner above mentioned, 

 has been observed by me only during the spring and part of the summer of the present year ; but 

 the results have been so satisfactory, that I can with the utmost confidence recommend the 

 machinery which I have described ; particularly when tender plants of any species are to be 

 raised in cold seasons of the year." 



{e) Without pledging ourselves to any opinion on the subject, we declare 

 frankly that we see nothing absurd in the idea of the finiit or the tubers of 

 a plant of the torrid zone being over-ripened in this country. We know 

 that the peach and the apricot, natives of Persia, are frequently over- 

 ripened, and also the melon ; any fruit or other production that may be 

 matured, may surely be over-matured. — Cond. 



(/) The passage alluded to is in a "Note hy Mr. Main^^ who can only 

 state that such was the general impression on his mindj he is however 

 glad to be corrected. — Cond. 



(g) The first reason (note a), being, as every reader who will take the 

 trouble to look at the passage will allow, an error of Mr. Knight, falls to 

 the ground; the remaining three are mistakes which any editor may make, 

 and which one would have supposed he might have atoned for, simply by 

 correcting them when they were pointed out to him, as we have now and 

 always done, and shall continue to do. — Cond. 



Errata. — Page 235. line 12 from bottom, for tm read //. Line 16. from 

 bottom, for " syllable " read " letter." 



