On the variations of Heat above and below ground. To the Editor of Recreations in Agriculture, &c. Woodbridge, May 3, 1800. SIR, I HAVE a long time wished to trouble you with a few lines upon a subject which has for many years engaged my attention; and I flatter myself that you will admit as an apology for calling your attention off matters of more importance, that an earnest desire of information leads me to seek, through your means, some communication with persons conversant in meteorological pursuits, from which my retired situation wholly precludes me. Last year I was induced to place a thermometer a few inches below the surface of the earth, from a desire of noting the increasing warmth of that element, and comparing it with the progrefs of vegetation; in short, a number of ideas, which I wished to confirm, or correct, led me to pay as much attention to this experiment as a very infirm state of health would permit. I shall not attempt to make any particular observations at present; but only request you to suggest to any person, that I shall be happy to commence a set of experiments in any way, or upon any plan that they may think most fit and convenient. The short time that I have been enabled to keep a register of the increase and decrease of the earth's heat, will be a sufficient reason for my abstaining from any conclusions; but at the same time there are some queries naturally arising from the variations that I have observed, which can be best answered by comparing registers kept in different si tuations, and for a considerable length of time. Light showers, lightning, a cold but drying wind after a heavy rain, cause a material alteration in favour of warmth: and continued dry weather with or without sun-shine has appeared after a time to diminish the warmth, or to render it a bad conductor of the heat of the sun's rays. A gentle shower produces almost an immediate change, and the accumulation of heat is considerable. I have made a hasty sketch of my mode of applying the thermometer. Sinking a flower pot into the earth with a bamboo perforated with numerous holes, I suspend the thermometer in the centre by a piece of cork or wood covered for three inches with woollen cloth, and which fits very closely into the bamboo, and excludes the air. The tube rises an inch above the bottom of the flower-pot, and is surrounded with fine sand level to its top; after the thermometer is thrust into the tube, I place another flower-pot, filled with the soil of the garden, and covered with woollen cloth, within this, which rests upon the sand, and fits sufficiently close to exclude the air. One pair I place in a strawberry bed, and another in an open spot of light earth; the depth about ten inches. Another I have introduced horizontally through a brick parapet wall which enclosed a part of the garden, and I was enabled to exclude the external air very effectually from this. The result was, that they tallied in both situations. Many variations may be made; and, as this is only a rude and undigested plan, I shall gladly pursue any other, and thankfully attend to any suggestions which you or your friends may do me the favour eite or afsist in the investigation of what appears hitherto to be considered (except by a very few individuals) in a very desultory way. I have added two specimens of an abbreviated journal; the hours I can readily vary as may be most convenient to others, and any form will be equally convenient to me; Barrington's appears as convenient as any. My desire is to obtain a series of observations, which, from previous arrangement, may correspond as to time of day and the mode of conducting the register, so far as to allow of comparing them with each other, though made in different and far distant districts. As my avocations confine me to one spot, and to very regular hours, it is my earnest wish to render myself of some trifling service in this department if it be possible. Profefsional engagements have of late, and will for some weeks much of my Occupy time, and must plead for the hasty letter which I now write you. A friend going unexpectedly from hence to-morrow induces me to snatch a favourable opportunity of getting this conveyed without expence. I am, sir, your obedient and humble servant, P. LATHBURY. VOL. III. T The highest and lowest degree of Thermometer daily from April 15 to 28, in the air and in the earth. . Highest. Feb. 1 to 10, 24 to 30, 21.30 40.25 25.35 22.34. 13, 50.37 45.35 Day. DAge. Hour. Weather. Wind. Sunday night. 1795. Jan. Sat. 24 Woodbridge, lat. 52" 12' 2h. A. M. Hazy. W. Sandy vale water running from N. W. to S. E. to the river Sun.25 3 Observations suggested by the above, by the Editor. It is with extreme pleasure that I give all the publicity I can to the above very liberal and ingenious proposal; which, if carried forward, cannot fail to be productive of consequences that may prove highly beneficial to science; how much so, no one can pretend to say; but even the few hints above given point at circumstances in physics that were not before suspected; and, if prosecuted, would probably bring into view many important facts that are not at all known. One circumstance that I think may possibly deter some persons from prosecuting this set of experiments, who might otherwise be inclined to do it, will be, the difficulty of making the observations with the apparatus above described. On which account, I wish it could be so altered, as better to suit those who have not inclination to subject themselves to much trouble. With this view, I beg leave to query, whether it might not tend to facilitate the observations, if the stalk of the thermometer were to be made so long as to have that part of it on which the degrees are marked rise so far above the surface of the earth, as to admit of being observed without being moved out of its place, whatever was the depth of the bulb? This part of it that rises above the ground might be covered by an inverted flower-pot, to prevent it from danger; or, which would be still better, by a wooden or tin case, with a small door to open, or windows for observing the variations. The bulb, in this case, might be closed round with the natural earth itself, without any extraneous body |