68 Intelligence and Miscellaneous Articles. 



it is sufficient to heat it to the highest temperature of the experi- 

 ments during a very long time relatively to the duration of the sub- 

 sequent experiments. 



Thus a thermometer which indicates the temperature of the 

 atmosphere, and from time to time is raised to 100° in order to fix 

 the value of the degree, is prepared for that use by three or four 

 days' heating to 100°. If, however, it is to serve for prolonged ex- 

 periments at temperatures near 100°, the whole length of it must 

 be heated to 100° for three or four weeks before graduation and 

 calibration. 



If a new thermometer is examined during this treatment, the 

 value of a degree is seen to change in the proportion of about 

 1 : 1*0004 ; and with the fixity of the zero towards the end of the 

 heating, the value of the degree is observed to have also itself 

 become fixed ; and it remains constant if the thermometer is left at 

 the ordinary temperature before a fresh determination of the 

 interval from 100° to zero*. 



I agree with M. Pernet in admitting that the value of the degree 

 does not change in ordinary observations, when there is no percep- 

 tible change in the position of the zero ; but a new thermometer 

 cannot undergo a great number of operations at 100° without one 

 or other of its constants varying. Thanks to the kindness of M. 

 Mascart, I have been able to submit to a long heating to 100° a 

 thermometer which had been in use during more than tan years ; 

 and with that instrument no notable change was seen to be pro- 

 duced in the position of the zero. The treatment at 100° does 

 nothing but imitate the effect of long use. The time necessary for 

 the treatment is abridged by heating for twenty-four hours in 

 boiling essence of turpentine, and afterwards from four days to a 

 week to 100°; and an analogous procedure serves for higher tem- 

 peratures. 



The glass must not be exposed to the corrosive action of boiling 

 water ; and metallic apparatus of easy construction permits those 

 operations to be effected without escape and without contact of 

 vapours of either water or mercury.— Comjotes Rendus de VAcaddmie 

 des Sciences, Nov. 13, 1882, t. xcv. pp. 910-912. 



THEORETIC INTERPRETATION OF THE EFFECT PRODUCED BY A 

 THIN LAYER OF OIL SPREAD OUT AT THE SURFACE OF THE 

 SEA TO CALM THE AGITATION OF THE WAVES. BY M. VAN 

 DER MENSBRUGGHE. 



Since the remarkable experiments of Mr. Shields in Scotland, 

 public attention has been called to the marvellous efficacy possessed 

 by oil for calming the surges of the sea. I have the honour of 



* It is to be noted that the thing required is to compare zeros de- 

 pressed to the maximum, and that the depression does not attain its limit 

 at 100° until after an hour or an hour and a half. The time necessary 

 to complete the depression diminishes with the elevation of the tempe- 

 rature. 



