THE FARMERS' REGISTER, 



525 



the coldest. We all Unow that the dahlias, pota- 1 

 toes, and Uidney-beans of the sheltered gardens! 

 in the valley of the Thames, are killed in the au- 

 tumn by frosts whose efi'ects are unleli on the low 

 hillsof Surrey and Middlesex.* Air J)aniell says 

 the has seen a difference of 30^, on i he same night 

 between two thermometers, placeii the one in a 

 valley, and the other on a genile eminence, in fa- 

 vor of the latter. Hence, he justly observes, 

 the advantages of placing a garden upon a gentle 

 slope must be apparent ; " a running stream at 

 its foot would secure the further benefit of a con- 

 tiizuous surface not liable to refrigation, and would 

 prevent any injurious stagnation of the air." 



In addition to this, it has been said that, to ob- 

 tain the most favorable conditions of climate in 

 this country, a garden should have a south-eastern 

 exposure. This, however, has been recommend- 

 ed, I think, without full consideration. It is true 

 that in such an exposure the early sunbeams will 

 be received ; but, on the other hand vegetation 

 there would be exposed to several unfavorable 

 actions. There would be little protection from 

 easterly winds, which, whether south-east or 

 north-east, are the coldest and driest th»t blow : 

 in the next place, an exposure to the first sun ol 

 the morning id very prejudicial to garden pro- 

 ductions that have been frozen by the radiation of 

 the night ; it produces a sudden thaw, which, as 

 gardeners well know,t causes the death of plants 

 which, if slowly thawed, would sustain no incon- 

 venience from the low temperature to which they 

 had been exposed.| It is probable, as I have 



* [A contrary etTect is experienced in the valleys 

 of our large rivers and lakes in the United States. 

 On the banks of the Hudson a margin of land from 

 half a mile to a mile in width on each side is very 

 effectually protected from the late spring and early 

 autumnal frosts ; while beyond that limit vegetation 

 is blackened by them. In autumn the warm vapor 

 which rises on a cold night from so large a surface 

 probably protects the adjacent shores : and even when 

 moderate frosts actually occur, the morning fog, which 

 lasts an hour or two, by softening the sun's lays and 

 causing a. gradual thaw, often prevents any injurious 

 result to vegetation. Some of our large inland lakes, 

 the surfaces of which are never frozen, have a decid- 

 ed effect upon the local climate, rendering it much 

 more mild than it otherwise would be. A. J. D.] 



t See Hort, Trans., iii. 43. 



X [In the northern and eastern sections of the union 

 many beautiful shrubs and plants, which are the or- 

 naments of our gardens in summer, but perish if 

 exposed to the rigorous cold of winter, are easily pre- 

 served upon this principle. The first impulse of the 

 novice in gardening is to place such half-hardy plants 

 (as the more delicate China roses, carnations, &c.) 

 in some warm sheltered spot, open to the genial rays 

 of the sun in winter ; a practice invariably followed 

 by their destruction. Our sun, even in mid-winter, 

 often shines with gieat brightness, and the thawing 

 and distention of the tissue of tender plants which 

 therefore follows, causes certain death. If, on the 

 contrary, the same species are placed in a cool shaded 

 aspect, or, what is preferable, if they are shielded 

 from the sun by a loose covering of straw, mats, or 

 even boards, ami thus kept from thawing except in 

 the most gradual manner, they will be found to have 

 sustained no injury whatever. We have seen a firge 

 number of the choicest camellias preserved without 

 any artificial heat through a cold winter, v.'hen the 

 mercury ranged below zero for several weeks, simply 

 by covering them with a common glazed frame, well 

 clothed with mats to exclude the direct rays of the 



el-'ewhere endeavored to show, that this singular 

 effect may be accounted lor as follows : — " In such 

 cases, it may be supposed that the air, forced into 

 parts not intended to contain it, is expanded vio- 

 lently, and thus increases the disturbance already 

 produced by its expulsion from the proper air ca- 

 vities ; while, on the other hand, when the thaw 

 is gradual, the air may retreat by degrees from ita 

 new situation without producing additional de- 

 iMtigement of the tissue. It is also possible that 

 leaves Irom which their natural air has been ex- 

 pelled by the act of freezing, may, from that cir- 

 cumstance, have their tissue loo little protected 

 trom the evaporating force of the solar rays, 

 which, we know, produce a specific stimulus of a 

 powerful kind upon those organs." {Hort. 

 Trans., n. s., ii. 305.) 



In our glazed houses, we have full control over 

 the state of the atmosphere, as regards both its 

 moisture and temperature, by means familiar 

 to every gardener ; but the manner of applying 

 those means, and the causes that oppose their 

 action, deserve to be the subject of inquiry. 



It will have been seen, li"om what has been 

 already stated upon that subject, that in general, 

 in warm countries, the air is occasionally at leasf, 

 if not permanently, filled wiih vapor to a much 

 greater extent than in northern latitudes*, and, 

 as in our glazed houses, we cultivate exclusively 

 the natives of warm countries, it is also obvioua 

 that, as a general rule, the air of such houses 

 requires, at certain periods, to be damper than 

 that of the external air. Those periods are when 

 vegetation is most active. On the other hand, 

 countries nearer the equator are subject to seasons 

 of dryness, the continuance of which is often 

 much greater than anything we know of here 

 in the open air, and consequently artificial means 

 must also be adopted to bring about, in glazed 

 houses, that state of things at particular periods ; 

 namely, those of the repose of plants. These 

 lacis afford abundant proof of the necessity of 

 regulating the moisture of the atmosphere with 

 due precision. 



Ijy throwing wafer upon the pavement of glass 

 houses, by means of open tanks of water, by re- 

 servoirs placed upon them by syringing, and by 

 other contrivances!, the quantity of water in the 

 air may be easily increased even up to the state of 

 saturation. But there are some circumstances, 

 easily overlooked, which interfere very seriously 

 with this power, and which, it may be cbnceived, 



sun, or prevent sudden variations of temperature. 

 For the same reason, orchards of peach trees in the 

 middle states, on the cold north sides of hills, are often 

 more vigorous and of greater longevity than those in 

 a full southern aspect : the heat of our summers being 

 sufficient to ripen their fruit and wood in such situa- 

 tions, while they are thus secured l>om the evils of 

 great and sudden changes of temperature in winter. 

 A. J. D.] 



* " Captain Sabine, in his meteorological researches 

 between the tropics, rarely found at the hottest period 

 of the day so great a dilierence as 10° between the 

 temperature of the air and the dew-point; making 

 the degree of saturation about .730, but most frequently 

 5° or .8.50 ; and the mean saturation of the air could 

 not have exceeded .910." {Daniell.) 



t A discharge of steam intp a glazed house has oc- 

 casionally been employed ; but the method requires 

 much attention on the part of the operator, and seems 

 inferior to"other contrivances. 



