150 ANNUAL OF SCIENTIFIC DISCOVERY. 



has shown the velocities actually attained by them in vacua. But 

 this vacuum is the absence of air only, not that of the " elastic me- 

 dium ; " and it is this that holds the poise of matter throughout illim- 

 itable space. 



NEW APPLICATION OF THE THERMOMETER. 



Every one accustomed to the use of the thermometer must be 

 familiar with the fact that it gives no account of the effects of various 

 temperatures, draughts, and damp upon the sensations. During one 

 of Mr. Glaisher's recent balloon ascensions a temperature of seven- 

 teen degrees was felt to be warm, because the voyagers had just quit- 

 ted a region where the instrument registered some degrees below zero. 

 So in leaving a room heated to eighty or ninety degrees, a temperature 

 of sixty degrees will be felt to be cold. It is one of the advantages of 

 the thermometer that it has no sensations, yet it would be an advan- 

 tage if we could sometimes use it to measure the magnitude of those 



^3 ^j 



influences which affect sensation as to heat and cold, and the mode of 

 so using it is very simple. A few years since Dr. Jonathan Osborne 

 communicated to the British Association some experiments on the use 

 of a heated thermometer as a means of instructing the physician as to 

 the influence of climate on health, but the subject was neglected, and 

 he has again called attention to it in an essay on the subject in the 

 Dublin Journal of Medical Science. One use of the heated thermom- 

 eter is to explain the difference observed in the effect on invalids of 

 climates having similar thermometrical characteristics. Thus the 

 western coast of Ireland has a mild and genial climate if tested by 

 the thermometer only, yet the trees are stunted in their growth by 

 the constant wind blowing from the Atlantic, and invalids do not 

 reap such advantages from a residence there as would be predicated 

 by trusting to the thermometer only. So, during a severe frost, if 

 the air is still, the cold is not much felt, but if there is a moderate 

 breeze or a gale, even with a moderate rise of the thermometer, the 

 sensation of cold is keenly felt, and, in point of fact, as regards health 

 and comfort, the temperature is lower, though the thermometer says 

 differently. The author thus describes the principle on which the 

 use of the heated thermometer depends : " The bulb being heated 

 up to ninety degrees Fahrenheit, represents the heat of the sur- 

 face of the human body; when in this state it is exposed to a cooler 

 medium, whether air or water, or mixture of both, as moist air, and 

 allowed to cool to eighty degrees Fahr. ; the time for cooling these 

 ten degrees represents (inversely) the cooling power exerted by that 

 medium, whatever it may be, or however applied. This cooling 

 power is derived from other agencies besides difference of tempera- 

 ture, as from radiation of the neighboring objects, conducting power 

 of the surrounding medium, and more especially from currents caus- 

 ing various proportions of it to be brought into contact with the heated 

 body within a given time. Now, these agencies have their combined 

 results exhibited in the degree of rapidity with which the cooling is 

 effected. Placed, as we are, in a medium, with few exceptions, always 

 below eighty degrees, we are constantly undergoing a process of cool- 

 ing, la our ordinary clothing we feel just comfortable at fifty-six 



