30 



REMARKS ON THERMOMETRIC REGISTERS. 



[1852. 



animal kingdom. The wolf, tlie bear, and the beaver hure dis- 

 appeared from Great Britain: tlie last public reference to the 

 latter, as among the ferce naturce of the British I.iles is, as we 

 learn from Mr. Daniel Wilson, in an act of King David I. of 

 Scotland, A. D. 1124; le&s than a century will doubtless see the 

 extinction of the same species, and some othei-s in Canada ; but 

 that which British naturalists and geologists cannot now determine 

 by direct endence, namely, whether a corresponding change of 

 climate has occurred, may be determined by our posterity if we 

 ■«-iU only take a little trouble in the matter. And let me not Ijc 

 met here by the old, but ingenious objection, that we are not 

 bound to do anytliing for posterity since posterity docs nothing 

 for us. Posterity does something for us. With posterity lie the 

 hopes and aspirations which are a part of the present rewards of 

 life : it is the guardian of our dearest interests, and we can no 

 more discmneet onreehes from the future than from tlie past. 

 However, in our circumst;rnces it is not altogether necessarj- to 

 resort to this argument to justify a reference to the present imper- 

 fect state of obsei'vation in Canada with a view to its impro.eraent. 

 We have, so to speak, side b}' side, in this extensive countrj', the 

 twelfth and nineteenth century. The nide beginnings of settle- 

 ment, where man shai'&s the soil with the wildest natives of the 

 forest, and nothing has as yet occurred to affect the physical 

 conditions of a state of nature ; and the fully developed empire 

 of his industry, where all the local changes likely to occur are 

 already wrought out. Can there be no comparison made between 

 these conditions ? It is perfectly possible, but unfortunately the 

 materials do not exist. 



Let us suppose the admirable example of the States of New 

 York, Ohio and Massachusetts, to be followed by the Canadian 

 Legislature, or, as it may be, by the different District Councils, 

 in the ajjpropriation of a sufficient sum to supply each District 

 Grammar School throughout the country with accurate meteor- 

 ological instruments; and that a careful register is kept at each. 

 There would then be about twenty points, in addition to those 

 already existing, at which the mean temperature for every month 

 of the year would in a few )'eai-s be known, and they would be 

 connected with a large number of stations in the States just 

 named. Situated, as the}' would be, at various ele\"ations above the 

 sea, a correction would be requisite to reduce them to the same 

 plane, and possibly, also, other corrections ; but these apphed, we 

 should have a series of stations which ought to furnish, with great 

 precision, the curves of equal monthly temperature, or the iso- 

 thermais, as they are termed, of the respecti\'e months, in this 

 region of the American continent. It would be not a little 

 curious and interesting to see these lines when drawn on the 

 map, varying their configuration, as they would probably do, if 

 the observations were jieifectly good, according to the character 

 of the country through which they might pass. To see, for 

 example, those belonging to the winter montlis bending to the 

 north, and those belonging to the summer months bending to the 

 south, when they emerged from an uncleared to pass through 

 a well settled district; to see in like manner the lines connecting 

 places having an equal annual fall of rain or snow, deflected from a 

 symmetrical coui-se by large areas of forest interpolated between 

 thriving settlements and open spaces. What the singular dis- 

 covery of the very thermometers used by Galileo, aud their com- 

 parison v/ith modern instruments, has not shuwn, because Italy 

 has long ago attained its permanent climatic condition, namely, 

 the effect of two centurie.s of improvement, might thus very possi- 

 bly be disclosed to our view in a dozen years, nor could any one 

 capable of the pleasure arising from the contemplation of natural 

 laws and operations fail to derive it here. It would be easy, but 

 is probably not necessary, to name other reasons why accurate 

 observations of the tliermometcr would bo highly valuable. I 

 pass tlierefore, at once, to the question as to wliat is necessary to 

 give observations this character. 



Almost every house possesses a thermometer, in very many 

 cases some sort of I'egular register is kept. A good many of 

 these registei-s, sooner or later, get printed. Can anything more 

 be required ? Alas ! a great deal ; nine out of ten of all such 

 amateur registers are not only worthlass, but mischievous and 

 deceptive, owing to the neglect of two simple precautions at the 

 outlet. First, — To get a good instrument: Secondly, — to 

 establish it in a proper position. 



1. Of Thermometers. — The common instruments purchased 

 for five or ten shillings at hardwai-e shops, are entirely unfit for 

 our purpose, on the grounds of inaccuracy and want of sensibilitv. 

 The best form of thermometer is one in which the bulb is cylin- 

 drical, or at least elongated, not globular, and blown extremel}' 

 thin ; each degi'ee, at least, should be marked on the scale ; in 

 the best instruments the degrees are subdivided; the graduation 

 for general Canadian use should extend from — 30° to +1 10° : 

 in Lower Canada it may occasionally be necessary to employ a 

 thermometer graduated below — 30°: mercury thennometei-s are 

 preferable to those in which the fluid is alcohol, from the property 

 which the metal possesses of varying in volume almost exactly in 

 proportion to the variations of temperature, such is not the case 

 with alcohol, which is also subject to chemical changes capable of 

 affecting its volume. The expansion of these fluids between the 

 freezing and boihng point of distilled water, the latter, under a 

 barometric pressure of 29.992, (760 millimetres^ is as follows: — 



Mercury :53'3o = 0.018018 Dulong and Petit. 



« J5'^ = 0.018153 Eegueault. 

 Alcohol Jg. ==0.111 



the volume of each at the freezing point of water being taken as 

 unity. The expansion of volume for one degree will be in pro- 

 portion, according to the scale we employ, and from these values 

 may be calculated the dimensions which the bulb of the ther- 

 mometer must have to render expansions of any degree of minute- 

 ness, which may be required, visible in the tube. In making stand- 

 ard thermometers of the highest character, the firet step is to 

 select a piece of glass tube, and to introduce it into a very small 

 quantity of mercury, filling about half an inch of its length. 

 By blowing gently through a flexible tube, this portion of mercury 

 is made to move onwards in successive steps each of its own length. 

 Shoidd there be any inequahties in the bore of the tube, as is 

 usually the ease, the same quantity of mercury will occupy some- 

 thnes a longer sometimes a shorter space; the exact space it 

 occupies is measured with all the precision possible in each jwsition, 

 marked on the tube, and afterwards subdivided as much as ma}' 

 be necessary. The scale is thus divided according to equal capa- 

 cities of the lore, a circiunstanoe obviously essential to the accu- 

 racy of the instrument A bulb being next blown on to the 

 tube the thermometer is finished in the usual way. The next 

 point is to determine the value of the divisions on the tube in 

 terms of Fahrenheit's or any other scale. This is done by first 

 immei'sing the instrument in a mixture of crushed ice with water, 

 ami noticing by the aid of a telescope, from a distance, the exact 

 dixision at which the mercury stands; then suspending the 

 instrument in a vessel of peculiar construction over boiling water, 

 and noticing in the same way the division at which it stands 

 when the air has been completely expelled from the \'6sscl, and 

 it is filled with steam whose elasticity is represented by the bar- 

 ometric ju'cssure at the moment. The temperature of such steam 

 reduced, if necessary, to the standard barometric pressure, is the 

 physical constant which philosophers have agreed to refer to for 

 the upper fixed point on the scale, that of freezing water beiuij 

 the lower fixed point; but there is a slight discrepancy in the 

 dati used in Englaml and in other countries. The standanl 

 barometric press\ne is 29,800 inches in England, measured on a 

 brass scale having a temperature of 62°, and 29,922 inches in 

 France, measured on a brass scale having a temperature of 32° : 



