October 3, 1902.] 



SCIENCE. 



547 



as those of our sensorium, it suffices that 

 the sun or the fire or some other agent, 

 whatever it were, that agitated more 

 vehemently its parts before, does either 

 now cease to agitate them or agitates them 

 but very remissly, so that till it be deter- 

 mined whether cold be a positive quality 

 or but a privative it will be needless to con- 

 tend what particular body ought to be 

 "esteemed the primum fngidiim.' The 

 whole elaborate investigation cost Boyle 

 immense labor, and he confesses that he 

 'never handled any part of natural phi- 

 losophy that was so troublesome and full 

 of hardships. ' He looked upon his results 

 but as a 'beginning' in this field of in- 

 quiry, and for all the trouble and patience 

 expended he consoled himself with the 

 thought of 'men being oftentimes obliged 

 to suffer as much wet and cold and dive as 

 deep to fetch up sponges as to fetch up 

 pearls. ' After the masterly essay of Boyle, 

 the attention of investigators was chiefly 

 directed to improving thermometrical in- 

 struments. The old air thermometer of 

 Galileo being inconvenient to use, the in- 

 troduction of fluid thermometers greatly 

 aided the inquiry into the action of heat 

 and cold. For a time great difficulty was 

 encountered in selecting proper fixed 

 points on the scales of such instruments, 

 and this stimulated men like Huygens, 

 Newton, Hooke and Amontons to suggest 

 remedies and to conduct experiments. By 

 the beginning of the eighteenth century 

 the freezing-point and the boiling-point of 

 water were agreed upon as fixed points, 

 and the only apparent difficulties to be 

 overcome were the selection of the fluid, 

 accurate calibration of the capillary tube 

 of the thermometer, and a general under- 

 standing as to scale divisions. It must be 

 confessed that great confusion and inac- 

 curacy in temperature observations arose 

 from the variety and crudeness of the in- 

 struments. Tliis led Amontons in 1702-3 



to contribute two papers to the French 

 Academy which reveal great originality in 

 the handling of the subject, and which, 

 strange to say, are not generally known. 

 The first discourse deals with some new 

 properties of the air and the means of 

 accurately ascertaining the temperature in 

 any climate. He regarded heat as due to 

 a movement of the particles of bodies, 

 though he did not in any way specify the 

 nature of the motion involved; and as the 

 general cause of all terrestrial motion, so 

 that in its absence the earth would be with- 

 out movement in its smallest parts. The 

 new facts he records are observations on 

 the spring or pressure of air brought about 

 by the action of heat. He shows that 

 different masses of air measured at the 

 same initial spring or pressure, when 

 heated to the boiling-point of water, ac- 

 quire equal increments of spring or pres- 

 sure, provided the volume of the gas be 

 kept at its initial value. Further, he proves 

 that if the pressure of the gas before heat- 

 ing be doubled or tripled, then the addi- 

 tional spring or pressure resulting from 

 heating to the boiling-point of water is 

 equally doubled or tripled. In other 

 words, the ratio of the total spring of air 

 at two definite and steady temperatures and 

 at constant volume is a constant, independ- 

 ent of the mass or the initial pressure of the 

 air in the thermometer. These results led 

 to the increased perfection of the air ther- 

 mometer as a standard instrument, Amon- 

 tons' idea being to express the temperature 

 at any locality in fractions of the degree of 

 heat of boiling water. The great novelty 

 of the instrument is that temperature is 

 defined by the measurement of the length 

 of a column of mercury. In passing, he 

 remarks that we do not know the extreme 

 of heat and cold, but that he has given the 

 results of experiments which establish 

 correspondences for those who wish to con- 

 sider the subject. In the following year 



