OF VENTILATION. 157 



influence of a free current of air upon ripening fruits ; 

 for I have never found ventilation to give the proper 

 flavour or colour to a peach, unless that fruit was, at 

 the same time, exposed to the sun without the inter- 

 vention of glass; and the most excellent peaches 

 I have ever been able to raise were obtained under 

 circumstances where change of air was as much as 

 possible prevented, consistently with the admission 

 of light (without glass), to a single tree." (Ebrt. Trans., 

 ii. 227.) 



It is not improbable that one of the advantages 

 of .ventilation depends upon a cause but little 

 adverted to, but which certainly requires to be well 

 considered. 



It was an opinion of Mr. Knight, that the motion 

 given to plants by wind is beneficial to them by ena- 

 bling their fluids to circulate more freely than they 

 otherwise would do ; and in a paper printed in the 

 Philosophical Transactions for 1803, p. 277, he addu- 

 ces, in support of his opinion, many experiments and 

 observations; of which the following is sufficiently 

 striking : — 



" The effect of motion on the circulation of the sap, 

 and the consequent formation of wood, I was best 

 able to ascertain by the following expedient. Early 

 in the spring of 1801, I selected a number of young 

 seedling Apple trees, whose stems were about an inch 

 in diameter, and whose height between the roots and 

 first branches was between six and seven feet. These 

 trees stood about eight feet from each other ; and, of 

 course, a free passage for the wind to act on each tree 



