Report of the Committee of Physics: Including Meteorology, on the Objects of Scientific Inquiry in Those Sciences

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R. and J.E. Taylor, 1840 - Geomagnetism - 119 pages
 

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Page 54 - The next correction, and in some respects the most important of all, is that due to the temperature of the mercury in the barometer tube at the time of observation. To obtain this every barometer requires to have attached to...
Page 54 - ... engraved conspicuously on some part of the instrument. Although all these corrections are necessary for the strict reduction of registered observations, they ought not to be applied to individual observations previous to registry. It is sufficient to know them. Their effect...
Page 58 - It should be allowed to do so for three or four minutes before the observation begins, taking care, however, not to let it mount into the bulb, by a proper use of the screw. At the same time the tube should be carefully cleared (by the same action) of all small broken portions of liquid remaining in it, which should all be drawn down into the bulb. When all is ready for observation, draw the liquid down to zero of its scale, gently and steadily ; place it on its stand, with its screen before it,...
Page 63 - ... that intensity of solar radiation which at a vertical incidence, and supposing it wholly absorbed, would suffice to melt one millionth part of a metre in thickness from the surface of a sheet of ice horizontally exposed to its action per minute of mean solar time...
Page 57 - Then, by alternate screwing and unscrewing the screw with the right hand, as the case may require, it will always be practicable to drive the air out of the cylinder into the ball, and suck down liquid, if any, from the ball, to supply its place, till the air is entirely evacuated from the cylinder, and the latter, as well as the whole stem of the thermometer-tube, is full of the liquid in an unbroken column. Then, holding it horizontally, face upwards, slowly and cautiously unscrew the screw, till...
Page 51 - ... hours, rather than not observe he may select his own, specifying only what they are at the head of every page of his register, and adhering steadily to them in practice, only observing to make the extreme observations of each day equidistant from the middle one. At the same time it will be borne in mind, that in what concerns the great Meteorological questions on which the most interesting features of the subject depend, the night is quite as important as the day, and has hitherto been far too...
Page 56 - ... flame, the mercury must be made to expand till it rises to the very top of the tube, and projects convexly into the air-bulb. The tube must then be placed upright, and, by tapping, the detached mercury will slip down beneath the steel index, and will fairly unite with the convex projection aforesaid. Now let the bulb cool, and the mercury will sink in one united column, and leave the index free. Besides the regular series of observations of the temperature of the air, there are other occasional...
Page 53 - Thus, when the mercury in the tube is above the neutral point, the difference between it and the neutral point is to be divided by the capacity, and the quotient being added to the observed height, the result will be the corrected height.
Page 54 - ... after at least an hour's quiet exposure, side by side, that they may have the same temperature. If compared by two observers, each should read off his own barometer in his usual manner, and each should take a mean of Several readings, then each should verify the other's results. By this means the zero of one standard may be transported over all the world, and that of all others compared with it ascertained. "The amount of the zero correction is often very large, as two or...
Page 43 - ... consequence of the electric discharge ? Opinion would seem to lean to the latter side, or rather, we are not aware that the former has been maintained or even suggested ; yet it is very defensible. In the sudden agglomeration of many minute and feebly electrified globules into one raindrop, the quantity of electricity is increased in a greater proportion than the surface over which (according to the laws of electric distribution) it is spread. Its tension therefore is increased, and may attain...

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