Leonard Waldo

“ Few are aware of the errors found to exist even in the thermometers of reputable makers. The well-known change which takes place with age in every thermometer not infrequently amounts to a degree and a half Fahrenheit within two years from the time the thermometer is made. The change depending upon the temperature to which a thermometer is heated, even supposing this to be no greater than the boiling-point of water, may be three fourths of a degree. ”

“ If we heat the thermometer to the boiling-point of water, and then immediately cool it and immerse it in melting ice, we shall obtain another point on the thermometer scale which we may call the temporary freezing-point, because it will gradually approach the permanent freezing-point, and after a few months, if the instrument is not again heated, it will finally coincide with it. ”

“ It is not unlikely that members of the medical profession have been sometimes misled by the readings of inaccurate thermometers, and they may have made such unfavorable statements regarding the chances of recovery of patients whose temperatures were high, that the patient, under the influence of his imagination, has given up the struggle for existence when a little more hopeful view of the case might have imbued him with fresh courage and led to ultimate recovery. ”

“ The determination of the freezing-points of standards is accomplished by the apparatus shown in Fig. 2, where a a' is a tinned-iron cylindrical vessel 9 x 9 inches, inclosing a smaller one 71⁄2 X 5 inches. A strainer allows the water from the finely crushed ice or snow to escape into the open space b', and the space between the outer and inner vessels is filled with cotton-wool. Close-fitting covers prevent currents of air from the outside, and when in use each thermometer is fitted to a cork which is imbedded partly in the ice. ”

“ Supposing that several thermometers, by different and equally skillful makers, have been prepared with the greatest care, it is found in comparing them that they differ sensibly among themselves, owing to the difference in the glass used in their construction, their varying sensitiveness to the slight changes caused by the circulation of the water in which they are immersed, and a variety of less obvious causes. ”

“ Standards require from a week to a month for their investigation, depending upon the degree of precision desired in the final certificates.
The official circular of the observatory contains detailed information relating to the supervision of hospital thermometers and the facilities offered to makers. There is no good reason why any maker should not furnish, with any thermometer sold, a certificate stating the errors of that particular instrument. ”

“ The theoretical mercurial standard thermometer to which this instrument has been referred, is graduated by equal volumes upon a glass stem of the same dimensions and chemical constitution as the Kew standards 578 and 584. The permanent freezing-point is determined, by an exposure of not less than forty-eight hours to melting ice, supposing the temperature of the standard has not been greater than 25° Cent. 77° Fahr. during the preceding six months. The boiling-point is determined from the temperature of the steam of pure water at a barometric pressure of 760 mm. ”

“ One boiling-point apparatus is constructed after Regnault's plan, and consists essentially of a brass stand (Fig. 3) supporting a water-tank w w', 6 inches in diameter and 3∙5 inches deep, upon which in turn rests a brass section of double tubing having an inside diameter of 5 and an outside diameter of 6 inches. This section, which extends upward 3·1 inches, has three open tubes each 0∙7 inch in diameter (v v') let into its outer wall. At the place which would be occupied by the fourth there is a small manometer-tube m, with a stopcock s, by which Fig. 2. ”