EXTRACT ON WARMING BUILDINGS BY HOT WATER. 291 



germination was visible, and in a month the plants are fit to trans- 

 plant into small pots. By this mode of growth the plants were not 

 liable to interruption from worms. The best time to sow seed is 

 from February to May ; the plants then get strong during the 

 summer. 



ARTICLE IV. 



EXTRACT ON WARMING BUILDINGS BY HOT WATER. 



In a former Number we noticed the very excellent " Practical Trea- 

 tise on Warming Buildings by Hot Water ; on Ventilation, and the 

 various methods of distributing Artificial Heat, and their effects on 

 Animal and Vegetable Physiology ; to which are added, an Inquiry 

 into the Laws of radiant and conducted Heat, the chemical constitu- 

 tion of Coal, and the combustion of Smoke. By Charles Hood, 

 F.R.S., F.R.A.S., &c." We then promised to give an extract from 

 it, to enable our readers more fully to appreciate so valuable a work. 



The cheapness of glass for horticultural purposes is now a strong 

 inducement to erect forcing and plant houses far more extensively 

 than heretofore, and the approaching season is very likely to be a 

 period of considerable increase in that particular. We therefore 

 respectfully suggest 'the propriety of consulting Mr. Hood's Trea- 

 tise. 



" One of the greatest advantages which the plan of heating by the 

 circulation of hot water possesses over all other inventions for dis- 

 tributing artificial heat is, that a greater permanence of temperature 

 can be obtained by it than by any other method. The difference 

 between an apparatus heated by hot water, and one where steam is 

 made the medium of communicating heat, is no less remarkable in 

 this particular than in its superior economy of fuel. 



" It seldom happens that the pipes of a hot-water apparatus can 

 be raised to so high a temperature as 212°; and, in fact, it is not 

 desirable to do so; because steam would then be formed, and would 

 escape from the air vent, or safety pipe, without affording any useful 

 heat. Steam pipes, on the contrary, must always be at 212° at the 

 least, because, at a lower temperature, the steam will condense. A 

 given length of steam pipe will therefore afford more heat than the 

 same quantity of hot-water pipe ; but, if we consider the relative per- 



