January 4, 1872. ] 



JOURNAL OF HORTICULTUBE AND COTTAGE GARDENER. 



Ijg compared with each other with far less chance of error 

 than has hitherto been the case. 



" Fig. 1 is a view of the stand. It is composed of white deal 

 boards, and can be constructed by any carpenter. It consists 

 of an oblong trunk t, 12 inches by 8 inches outside measure, 

 to the opposite sides of which trunk are uaUed boards, b, b, at 

 the distance of three-quarters of an inch, and projecting about 

 6 inches from the trunk towards the north. Outside of these 

 are nailed other thin boards, c, c, full half an inch distant, and 

 projecting about 4 inches beyond the last-mentioned boards, 

 also towards the north. These sides being thus multiple, 

 prevent the sun from heating the interior of the stand, where 

 the thermometers are placed. The top or pent-board, p, is 

 made double, and the boards are placed fuDy three-quarters of 

 an inch distant from each other, and come so forward as to 

 overhang by a fuU inch. The legs, L, L, of the stand are 

 merely the continuation of the sides of the trunk. The boards, 

 or feet, r, F, are loaded or fixed to the ground to sustain the 

 force of the wind. The interior, T, is blackened to prevent 

 strong reflections of light. 



" Fig. 4 is a ground plan, or bird's-eye view of the machine. 

 The sides and woodwork generally are of three-quarter-inch 

 "White deal. The distance or space between the sides of the 



trunk, T (Jig. 1), and the board or inner bide ( ti;h i), is three- 

 quarters of an inch ; and the distance from that board to the 

 outer side {fig. 4), is full half an inch. The narrow boards 

 (fig. 4), are to be uaUed, with studs intervening, to the middle 

 board or side, and are for the purjiose of preventing the sun 

 from shining between the trunk and the sides of the stand, 

 when near the meridian. The sides are fixed one upon another 

 at the required distances — viz., three-quarters of an inch and 

 half an inch, by numerous wooden studs, partially shown at 

 figs. 1 and 2, about three-quarters of an inch diameter, and 

 the screws passed through the sides and studs, fixing the 

 whole firmly together. The whole is to be painted white, except 

 the trunk t, which should be black. 



" Fig. 2 is the view of the north side of the stand. No. 1 is 

 an index thermometer to give the greatest cold of the night. 

 The thermometer inclines, the ball end being the lowest, in 

 order that the index, by being assisted by gravity, will move 

 more easily. No. 2 is an index thermometer to show the 

 greatest heat of the day ; for the same reasons it is also placed 

 on an incline, the ball being the highest. No. 4 are a pair of 

 thermometers called the wet and dry-ball thermometers, to 

 show the power of the air to evaporate water, v Is a vase or 

 cistern of water for the wet-ball thermometer ; it is placed oa 



Fio ■>. 



the outside of the thermometer, to which a cotton wick is to 

 be attached to connect it with the water, and at about the same 

 ■elevation as the ball of the thermometer, in order that the 

 evaporation from the vessel of water may not influence the 

 thermometer on the other side, which is to be the dry-baU 

 thermometer ; for, in some careful experiments which I made 

 •with a vessel placed beneath the balls, it was found that the 

 dry ball was lowered from 0.2' to 0.3°, which, though ap- 

 parently a small error, is a serious amount in the main dif- 

 ference between the readings of the dry and wet-ball ther- 

 mometers. 



" Fig. 3 is the view of the south side of the stand. No. 3 is 

 iin index mercuriiU thermometer, with a black ball to give the 

 greatest solar heat, r Is a rain gauge on Glaisher's con- 

 struction ; and B is a measure into which rain is to be poured 

 for measurement." 



For ascertaining the temperature of the soil at various 

 depths, we recommend three tin tubes to be sunk in it in a 

 place fully exposed to the sun, but far from a wall or other 

 shelter ; each tube to be about 2 inches in (hameter, and of 

 the respective depths of 2J feet, IJ foot, and 9 inches. These 

 tubes should have in each a thermometer with the shank 



lengthened so as to correspond with the depth of the tube in 

 which it is placed. These tubes should be covered over by 

 a hand-hght glazed only on the top to exclude rain from 

 entering the tubes, but entirely open at the .sides to allow of the 

 free admission of the air. The thermometers should be well 

 packed into the tubes with cotton to exclude the atmospheric 

 temperature. 



The importance of ascertaining for a certainty that the soil 

 is of a temperature correctly relative to that of the air above 

 it is demonstrated by the fact, that naturally its average tem- 

 perature is always higher than that of the au-. In other 

 words, the roots on the average are kept warmer than the 

 branches. 



From observations made at Chismck during six years (1833— 

 1847), Mr. Robert Thompson gave the following epitome of 

 results : — 



" The hottest year as regards the temperature of the earth, 

 1846, afforded a mean temperature of 52.32" at 1 foot deep ; 

 and 52.85° at 2 feet deep. In the coldest year, 1845, the 

 mean temperature at 1 foot deep was 48.95° ; and at 2 feet 

 deep 49.44°. The respective differences of the two thermome- 

 ters in these hottest and coldest years were 3.37° at 1 foot 



