202 MANAGEMENT OF THE CKP'sTNUT TREE. 



lil^^.i^jt- ®" hypothesis, th^t cannot be admittt^d. On the sn!)ject of 

 poitio;;. proportion, Mr. Dalton's views, give the happiest explana- 



tion; but they must be acknowledged to be hypothetical. 

 The particles of bodies are objects of science, and not of 

 sense; yet we speak of them, as if they were as palpable 

 and visible as the masses they compose- 



I shall conclude these observations by an allusion to two 

 ■jnstrtncts of combinatioiij which have not, I think, been very 

 TTilion of oss^ satisfactorily explained. The first is the un'on of gasses on 

 sesoniheap- the application of heat ; the second, the same combination 

 LaTI^I by ^y means of compression. They are both explained on the 

 consi'lttiiicaj. mechanic^il principle of an approximation of the particles, 

 occasioned by the compression ; but it is to be remembered, 

 that, as bot!) operations may be attended by compression, 

 they are also both attended by an increised temperature. 

 May not the heat have some more immediate operation in 

 attracting these combinations, than is supposed : I believe 

 the pressure, which causes the gasses to combine, requires 

 to be applied very suddenly, so that a due quantity of heat 

 may be evolved. It is requisite, that the application oFheat 

 to inflame gasses be applied suddenly, so as to ensure a 

 considerable compression? The determination of both 

 these questions by experiment would be extremely interest- 

 ing. The influence of compression is seldom or never re- 

 sorted to in pneumaiic experiments ; although it would un- 

 doubtedly prove an agent of considerable power in promot- 

 ing combination. 1 am, Sir, 



Yours respectfully. 

 University, EdhJnirgh, MARSHALL HALL. 



September the '■25ih, 1811. 



IX. 



On the Horticultural Management of the Sweet or Spanish 

 Chestnut 'tree. By the Right Hon. Sir Joseph Banks, 

 Bart, K. B. ^c* 



Chestnuts J^ jsi all the northern parts of Europe, where chestnuts are 

 grafted on the • o ,. i , ■ /. <• • i , i 



coatmem, xx^^d tor food, tiie practice of gratting the trees that bear 



♦ Tran?. of the Horticultural Society, vol. I, p. 140, 



theiia 



