128 Pom's Mode of ventilating and iioarmiyig Hot-hoitses. 



not succeed, for want, among other causes, of efficient ventilation, 

 combined with adequate heat; but by Mr. Penn's plan all dif- 

 ficulty on that point will be readily overcome. Suppose, how- 

 ever, that the plan had no other advantages than that of rendering 

 the air of orchidaceous houses and stoves agreeable to the 

 feelings, instead of being oppressive and unbearable; that result 

 alone would be sufficient to constitute it one of the greatest im- 

 provements that have hitherto been made in the production of 

 artificial climates for plants. 



In conclusion, we have only strongly to recommend all such 

 persons as may be disposed to try Mr. Penn's plan, to apply to 

 Mr. Penn himself; not only because he must necessarily under- 

 stand his own plan better than any other person, but that, being 

 an independent man, and most eager for the celebrity attendant 

 on the dissemination of his plan, he is most likely to carry it into 

 execution cheaper than any other tradesman can do. Indeed, 

 Mr. Penn authorises us to state that he will carry his plan into 

 execution any where in the United Kingdom; and, after a year's 

 trial, if it should not give entire satisfaction, he will take the ap- 

 paratus back again, and replace whatever apparatus may have 

 been there before, entirely at his own expense. We are the 

 more particular in stating this, because, from the circumstance of 

 Mr. Penn's not having taken out a patent, and the invention 

 being likely to come into universal use, there will, as in the case 

 of Arnott's stoves, be numbers of imitators, and pretenders 

 to improvements, who do not understand even the first principles 

 on which the arrangement acts. With the most noble and dis- 

 interested views, and apparently, also, with views the most ju- 

 dicious with reference to the public good, Dr. Arnott left his 

 improvement open to the competition of every ironmonger; in 

 consequence of which, every ironmonger constructed Dr. Arnott's 

 stoves, and by far the greater number of them spoiled them. It 

 would have been much better for the public had the doctor 

 taken out a patent. We wish Mr. Penn had done so ; but, since 

 he has not, we consider it our duty most strongly to warn the 

 public against employing others to execute the plan of an inventor, 

 when they can get it executed by the inventor himself, and that 

 with the advantages above stated. We have only to add that 

 Mr. Penn undertakes to construct all kinds of hot-houses, whether 

 of timber, or of iron or other metal. — Bayswater, Feb. 8. 184'0. 



Art. X. Mr. Wilmofs Opinion of Mr. Penn's Mode of heating and 

 ventilating Hot-houses. Communicated by Mr.WiLMox, F.H.S.,&c. 



As you have written to me on the subject of Mr. Penn's prin- 

 ciple in heating hot-houses, pits, &c., and expressed a wish for 

 my opinion thereon, I will endeavour to convey it in a few words. 



