500 Qiicries and Answers, 



an}' other correspondent, to account for the phenomena which I shall pro- 

 ceed to detail. 



In tlie parish of Great Missenden, in the county of Buckingham, and 

 on the south-eastern slope of the Chiltern range of chalk hills which inter- 

 sects the county, rises the Missliiu'ne stream : it runs in a southerly direc- 

 tion along a wimling valley of about fifteen miles in length, and falls into 

 the river Colne at Denham. In its course, it works the mills at Amers- 

 ham, Chalfont St. Giles, Chalfont St. Peter, Oakend, and Denham. It is 

 liable to fail in summer; and, what is remarkable, the mills nearest its 

 source, and those nearest its junction with the Colne, are often in full 

 work when the intermediate mills are standing still. This is owmg to the 

 greater portion of the water sinking beneath the base of the chalk ibrm- 

 ation about a mile below the town of Amersham, and rising again, by 

 numerous springs, in the valley, about a mile below the village of Chalfont 

 St. Peter. At the spot where the springs burst forth, the valley is con- 

 tracted, the level bottom being only about a quarter of a mile wide. The 

 brows on each side rise somewhat abruptly : that on the west side, to the 

 height of 103 ft., while the opposite side is about 10 ft. lower. At all 

 seasons, a copious exhalation, or rather evaporation, fills the valley to 

 the height of between iO ft. and 60 ft. above the level of the stream at 

 this place : often quite visible in frosty weather ; and sensibly felt during 

 summer, by reason of the difference of temperature in passing down to, 

 or rising from, the bottom of the valley; the heat within the body of 

 vapour being always from 7'^ to 10^ lower than the superincumbent clear air 

 above. The heat of the soil in the bottom of the vallej', at 1 ft. beneath the 

 surface, is never lower than about 40° of Fahrenheit ; and increases hij,her 

 and higher the deeper an excavation is made. The water in the stream is 

 never frozen, even when the thermometer stands at zero in the open air. 

 The temperature of the soil, on the top of the banks at the same depth, 

 varies according to that of the air, but is generally a few degrees higher in 

 winter ; and, like that in the valley, many degrees colder in summer. 

 During the heat of the latter season, vegetation is most luxuriant, and 

 dews are most copious in the valley; but the plants are tender, both the 

 flowers of fruit trees, and the foliage of common shrubs, being frequently 

 destroyed by spring frosts. On the higher ground on each side, the con- 

 trary of all this is seen : plants grow slowl}', but they are hard}'; dews are 

 less frequent, and comparatively light ; and, while potatoes, French beans, 

 shoots of asparagus, &c., are destroyed in the valley, no such effects are 

 experienced on the hill. 



I have been rather particular in detailing the cuxumstances of the 

 place, and the effects of weather on vegetation, in order that Mr. Murray 

 may be enabled to explain to us the causes of the effects above stated, 

 and to what we should ascribe the lower temperature of the valley : whe- 

 ther to evaporation, radiation, or to chilled air which has slid down from 

 the high grounds above. 



I would only beg to observe, that radiation from subterranean heat 

 should not be forgotten in this enquiry, as it is probably owing to this that 

 the dews and evaporation of the valley of the Missburne are so abundant. 

 1 am. Sir, yours, &c. — Querist. July, 18.33. 



Technical Terms in Horticultural Chemistry, and a Test for detecting the 

 Oxide of Iron in Soils. (Vol. VIII. p. 735.) — Sir, Your worthy corre- 

 spondent, Mr. Taylor (Vol. VIII. p. 735.), wishes " some of your learned 

 correspondents would insert in your Magazine a list of the chemical terms 

 relating to horticulture, which are not found in an English dictionary, and 

 with their proper accentuation." Such a contribution, he thinks, would be 

 useful to such as are not acquainted with the learned languages. No one 

 can deny, and it gives me pleasure to see, that you do every thing in your 

 power to impress it upon the minds of your readers, that a knowledge of 



