260 Further Improvements in the Mode 



incisions, leaving the tops of the vines entire ; the inserted 

 grafts soon vegetated, and became lateral branches, and were 

 the only parts of the vines which showed the least signs of life, 

 for months after their insertion. If those grafts derived the 

 vegetating power from the stock of the old vines, it is an un- 

 accountable circumstance that no other part of the vines vege- 

 tated before the approach of the next forcing season. 



This fact alone is quite sufficient to show that the present 

 notions on this branch of the botanical system are incorrect 

 and erroneous. Yours. &c. 



Welbeck, April, 1829. Joseph Thompson. 



AuT. VI. Further Improvemeyits in the Mode of heating Hot- 

 houses by hot Water. By Robert Bvers, Esq. 



Sir, 

 Since I had the pleasure of addressing you, on the hot- 

 water system, many improvements have occurred to me, arising 

 from various causes, the principal one, that of having my small 

 houses and pits to remove to this place, and to re-erect; also, 

 from the numerous communications which I have received 

 in consequence of my letter to you. As space in your Magazine 

 is valuable, I will not explain how, or why, these plans oc- 

 curred to me, but at once attempt to detail them, first giving 

 what I consider the proper powers of a hot-water apparatus, 

 and, without these powers, it does not appear to me that it 

 can fully answer the purposes of the horticulturist with cer- 

 tainty : 1. It should have the means of producing rather more 

 heat than may be required ; 2. of applying that heat at plea- 

 sure, and in a very short time ; and 3. of retarding that heat 

 when necessary. These properties are certainly to be obtained 

 by the use of water, and, as a general guide, every apparatus 

 should, when in full work, have the power of raising the tem- 

 perature of the house, frame, or pit, from 45° to 55°, or even 

 60° ; granting it has this power, and the thermometer sinks 

 to 20° out of doors, the temperature in your house will be 

 65° to 80°, which I conclude sufficient for all winter forcing. 



For some time I have been anxious to determine the exact 

 quantity of heat given out by each foot of pipe of a given size, 

 at a certain temperature ; or, in other words, how many cubic 

 feet of air can be raised to a required temperature by a given 

 quantity of water, say at 120° of heat. Perhaps some of your 

 mathematical readers may be induced to make the experiment 



