50 REPOKT— 1873. 



a permanent set, wliicli was great at first (in an untried material), but became less 

 by repetitions of the experiments. 



With hard lianuuered german silver the set at Jirst much exceeded that of steel, 

 being equal to one-third of the compression, but after four repetitions of the expe- 

 riment amounted to only one twenty-seventh. This metal, unlike steel, indicated 

 equal deflections -with equal degrees of heat, showing that, in instruments where it 

 could be used, no secondary compensation would be required, because the ratio is 

 6 ;£ual for mean aud extreme temperatures. 



These experiments demonstrate, in regard to any instrument for indicating and 

 registering weight, pressure, temperature, or time by means of the law of elasticity, 

 the importance of subjecting the material (whether steel, glass, or particularly any 

 metal in which this property is obtained by condensation or hammering) to an 

 excess of temperature before the graduations and adjustments are made. 



On a New Form of Rutherford's Minimum Tliermometer, devised and con- 

 structed hy Mr. James Hicks. By G. M. Whipple, B.Sc, I.B.A.S., of 

 the Kew Observatory. 



INIany different kinds of thermometers have been constructed for the purpose of 

 indicating the lowest temperature of the air during a given time ; but none has been 

 found to fuliil the desired object so well as the common or Rutherford spirit- 

 thermometer. 



The chief objection to the use of this instrument is found to be in the fact that 

 the spirit-thermometer cannot follow sudden variations of temperature so quickly 

 as the mercurial thermometer ; hence, on occasions when rapid changes occur, the 

 indications of the two instruments are not accordant. 



In the thermometer exhibited Mr. Hicks has in a great measure succeeded in 

 overcoming this difficulty by the device of largely increasing the surface of the bulb 

 exposed to the air, whilst at the same time he greatly reduces its cubical contents. 



In 1862 Mr. Beckley suggested the formation of thermometer-bulbs on the pat^ 

 tern of certain bottles, in which the bottom is forced up a long way into the body, 

 and Mr. Hicks constructed a mercurial thermometer, which was shown in the In- 

 ternational Exhibition. Practical difficulties, however, obstructing the manufacture 

 of this kind of thermometer, very few have been made. Recently Mr. Hicks 

 endeavoured to make spirit-thermometers upon the same principle, and having 

 succeeded can now construct bulbs in the form of a hoUowed-out cylinder, with the 

 film of spirit reduced to any degree of tenuity. 



In order to determine the relative advantages of the old- and new-pattern ther- 

 mometers, experiments have been made at the Kew Observatory, which show that 

 the time Hicks's minimum thermometer requires to fall through 25° Fahr. is 

 55 seconds, whilst a common spherical-bulb minimum takes 2 minutes 25 seconds 

 to fall through the same extent of scale ; and Hicks's rises 25" in 57 seconds, the 

 other thermometer occupying 2 minutes 24 seconds to rise through the same in- 

 terval. 



An improved form of the instrument has the bulb in the form of a double tube 

 open at both ends, allowing free passage of the air through it. 



Oyi a New Electrical Anemograph. 

 By G. M. Whipple, B.Sc, F.R.A.S., of the Kew Observatory. 



Amongst the numerous instruments which have been devised for recording con- 

 tinuously and automatically the velocity and direction of the wind, none has met 

 with more general adoption than the form known as the Beckley or Kew-pattem 

 Anemograph. 



This instrument was originally constructed in 1857, by a grant from the British 

 Association ; and a detailed description of it, with Plates, is to be found in the Report 

 of the Association for the year 1858. 



Some minor modifications found necessary having been introduced into the in- 

 strument, it was accepted by the Meteorological Committee ; and it is now employed 



