ON THE EXPOSURE OF PLANTS. 99 



These low grounds are nearer the main springs, and often abound 

 with them, whence exhalations are ever rising, though imper- 

 ceptible ; of course such a valley must always be more chilly, and 

 more subject to keen frost than any drier or more elevated si- 

 tuations. Such glens, provided they are open to the south, are 

 chosen as the most suitable for tender exotics, merely because 

 they are more sheltered from the northern blast. In the summer 

 indeed, such a locality is most favourable to the quick and strong 

 growth of every plant. The air, being generally calm and moist, 

 conduces to vigorous expansion ; and the very coolness of a sum- 

 mer's day or night, as felt in such places, is most propitious to 

 luxuriant vegetation. These circumstances, however, instead of 

 being beneficial to tender exotics, have a directly contrary ef- 

 fect ; the summer excitement only renders them less able to bear 

 the frosts, which fall upon them with redoubled intensity in winter. 

 And instead of the slow and sturdy growth which would have hap- 

 pened to a plant on a dry and breezy hill, or on a northern as- 

 pect, we have an enfeebled nursling, unfit to bear the rigours of 

 our climate from sheer mismanagement, 



Many proofs of the truth of these statements may be adduced, 

 but we presume they are unnecessary, as the facts must have been 

 repeatedly observed by our readers in general. The fact, how- 

 ever, is most important, not altogether for the sake of naturalising 

 exotic plants, but for fixing the sites for gardens and orchards, 

 which, if misplaced at first, give cause ever after for regret. 



Not only dq the exhalations from a moist valley generate cold, 

 but the cold air which descends upon the hills after sunset is said 

 to " slide down" and settle in the lowest place. So firmly is 

 this believed, and acted on by a well-known horticultural phi- 

 losopher, John Williams, Esq., of Pitmaston, near Worcester, 

 that in all cases where a garden is made on ground sloping to the 

 south, that gentleman invariably advises the lowest boundary to 

 be a hedge ; or if a wall, it be raised on grated arches high 

 enough to allow the escape of the cold fleece of air accumulated 

 within the garden. On the same principle, whatever may be 

 the aspect, the upper boundary wall should be high and close, 

 to intercept the descending current and divert it round the 

 ends. 



From these circumstances, then, it is fair to conclude that low 

 situations should never he chosen for garden sites, or as the bes{ 

 places for tender exotics. 



