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REMARKS ON DRAINING. 



the tube of the instrument expands the fluid and indicates an 

 elevation of temperature, although none takes place in the medium 

 in which the bulb at a is situated. There are rules for correct- 

 ing- the expansion which occurs in such cases, but they are very 

 complicated. 



We have now seen that water exerts an enormous pressure even 

 at the depth of a foot ; what effect this of itself may have on the 

 health of plants I do not pretend to know. It expels air and 

 other gases, the food of plants, from the vicinity of the roots, 

 and all agree that in this respect it must be considered injurious. 

 It prevents heat from being carried down to the roots ; and when 

 these are chilled they cannot support a healthy vegetation. 

 Finally, it is more stagnant in summer than in winter ; the re- 

 tentive nature of the soil, where saturation exists, prevents water 

 of any temperature from moving downwards ; but the colder 

 will displace the warmer. For example, water at 47° having 

 possession of a retentive soil in spring, will not change its posi- 

 tion in consequence of the fall of warm rains during summer. 

 Unless carried off by evaporation it will remain stagnant during 

 the warm season, and will only give place to winter rains, or 

 those that may supply colder and heavier water than itself. 

 Stagnant water is known to be very pernicious to the health of 

 plants, excepting to that of some species naturally adapted for 

 growing in it. As proof that the roots excrete, it could be told 

 in many cases from the smell of the soil what plant had been 

 growing in it ; and if roots are long in stagnant water it becomes 

 impure. Want of drainage, therefore, deprives the roots of 

 proper nourishment, subjects them to a chilling temperature, and 

 forces them to absorb a vitiated fluid. 



I now proceed to give an account of the beneficial effects of 

 draining, as instanced in the case of an orchard belonging to 

 Robert Manning, Esq., situated on Norton Heath, near Black- 

 more, Essex, about seven miles north-west from Ingatestone. 

 The ground lies high, and is naturally a retentive marly clay — 

 red when burned. The extent inclosed is about three acres. It 

 was planted in 1828, with apples, pears, plums, cherries, and 

 filberts. The trees were 12 feet apart each way, and intended 

 to be trained as dwarfs. Mr. Manning's object was to possess 

 specimens of the very best sorts for private use for himself and 

 friends, and after that to look only to profit. The ground had 

 but a shallow trenching. The trees grew tolerably well for 

 some time, but after seven years they began to exhibit symptoms 

 of ill thriving, and were every year getting worse : I saw them 

 in 1840, and instead of increasing in size they appeared to be 

 decreasing. In 1841, Mr. Manning states that the absence of 

 growth was such that he could not find scions to regraft some 



