Retrospective Criticism. 2S3 



municate with the transverse drains in the interstices of the tubes. They 

 succeeded with great difficulty in keeping out the frost during the late severe 

 winter, and now the season is further advanced, and the weather more clement, 

 the plants and vegetables look remarkably well, reflecting great credit on Mr. 

 Saunders, the gardener, who is a young man particularly assiduous and per- 

 severing in his habits, and of very superior ability. 



It must be distinctly understood that no perceptible current of revolving air 

 was ever discovered either in this or the former-mentioned structures, during 

 the closed state of the sashes, (naturally an ascent of heated air from the 

 tubes to their vertex, amounting, perhaps, to an agitating current, but no re- 

 volution,) consequently ventilation was resorted to, and is continued in the 

 usual way, and it is expected, before another winter ensues, the pipes will be 

 exposed, and thus a due chance of the requisite emission of heat afforded them. 

 It was glazed by Mr. Drake, with British sheet glass, which gives it a re- 

 markably neat and elegant appearance ; but the laps being entirely closed with 

 putty, or other cement, an immense drip of condensed vapour is the con- 

 sequence, which evil, it is thought, will lead to the tedious expedient of 

 reopening the laps. — G. C. March 11. ISll. 



On this communication we have to observe that we recommended Mr. 

 Penn's mode of heating on the following grounds : 1. because it had attained 

 what always has appeared to us a very desirable object in hothouses (see 

 Encyc. of Gard., edit. 1824, p. 313.), the complete circulation of the air 

 within, without admitting any air from without, and without diminishing its 

 moisture : 2. because Mr. Penn authorised us to state (see our Volume for 

 1840, p. 128.) that, in any case in which he was employed, if he were not suc- 

 cessful, he would reinstate the houses as he found them, at his own expense ; 

 so that no gentleman by trying his plan could be any great loser : and 3. 

 knowing Mr. Penn to be a man of probity and property, we felt confident, as 

 we now do, that he would be able, as well as willing, to keep his word. 



That Mr. Penn has not been successful either in producing sufficient heat, 

 or in effecting a complete circulation of the air, in more than one instance, is 

 a fact which cannot be denied ; but, as he has been most successful in the 

 case of his own houses, and also in those of Mr. Wilmott, the fault is evidently 

 not in the principle, but in its application. Having brought Mr. Penn's 

 system into notice, however, we must leave it to work its way among other 

 systems ; and, though we are satisfied that the circulation of the air in hot- 

 houses is an advantage, and that the system of cross drains which Mr. Penn 

 adopts is the best hitherto devised for this purpose, yet we by no means ex- 

 pect that every gardener is to agree with us in opinion. We know that there 

 are some who set little value on the circulation of air among plants, except in 

 the case of setting fruits ; but we have never been among that number. In- 

 dependently of the plants, the advantage of a circulation, in all houses which 

 are to be walked into in order to examine the productions, will not, we think, 

 be denied, except by those who wish to deprive Mr. Penn's system of all 

 merit whatever. Were Mr. Ashton Smith's conservatory ours, we would try 

 Mr. Penn's system two or three times, before we would give up the advantages 

 of air in motion to walk in. 



It will be seen by a previous communication from Mr. Penn, as well as in 

 the article by M. N. T., in our January Number, p. 42., that Mr. Penn has 

 made several improvements in his arrangements, one of the greatest of which 

 is placing the pipes in front, and another is placing those in the middle of 

 span-roofed houses in an uncovered drain or box, with which the cross drains 

 communicate. With respect to a passage in the above communication in 

 which the writer speaks of" the impracticability of keeping the sashes screwed 

 down, as advised, during a scorching summer's day," vie can only say that, if 

 any thing of this kind has been advised by us, we are in error; if Mr. Penn 

 has advised it it is rather singular, because in the summer season he always 

 opens the top sashes of his own houses. If the writer alludes to us, it must 

 be to the following passage : " When it appears desirable to change the air of 



