141 REPORT — 1861 



being maintamed in this way at a perfectly uniform temperature, will oppose a 

 uniform elastic force against the column of mercury, which latter, being removed 

 from all atmospheric influences, fau-ly represents the gravitation of the earth. 



In moving this insti-ument fi,'om shallow water upon a sea of 1000 fathoms depth, 

 the mercury column would rise -j-s^j-jth part of its length in the second bidb ; but 

 before any sensible alteration has taken place in the merciuy level, the upper surfiice 

 of the spirits of wine terminating in the narrow tube will have risen sufficiently to 

 restore the balance of pressure, and the spirits being twentj' times lighter than 

 mercmy, the scale of observation will be increased twentyfold. Lut the spirit 

 cokmm, in rising, displaces oil of veiy nearly the same specific gravity, which 

 causes another increase of scale at least twentyfold. By these means a scale of 

 3 inches per 1000 fathoms of depth is obtained. 



An instrument of this description was tried, by pennission of the Admiralty, and 

 although it was still imperfect in some respects, its indications agreed generally 

 within 10 per cent, with the results of actual soimdmgs. In the course of the in- 

 teresting discussion which ensued. Professor Tyndall suggested that the instrument 

 would be equally applicable for measuring heights, and he proposed to try it with 

 Mr. Siemens on the Cumberland Hills at some future time. 



On a Neiu Minimum Mercurial Thermometer proposed by Mr. Casella. 

 Bt/ Baifoitr StewatvT, A.M. 



Branching off from the side of the stem of this insti-ument and connected with 

 the capillaiy bore, we have a chamber the diameter of which is much wider than 

 the capillary bore. This chamber is abruptly attached at its extremity to another 

 chamber of smaller bore than itself, but still mder than the capUlary tube. 



To set this instrument, incline it slightly until the mercury in the side chamber 

 comes to the abrupt termination between the two chambers. The mercuiy in the 

 capillary tube will now denote the true temperatiu'e. Let this be G0°. If the 

 temperature rise above 60°, the rise wUl take place in the side tube, and if it then 

 begin to fall, the fall will also take place in the side tube until it reaches 00° ; but 

 below that the fall will take place in the capillary tube, as there is a disinclination 

 of the mercury to recede from the abrupt termination between the two chambers 

 towards the capillary tube. The instrument thus acts as a minimum thermometer. 



On British Bain-fall. By G. J. Stmohs. 

 The author directed attention to the very contrarj^ statements current on the ques- 

 tion — Is there any secular variation in the amount of British rain-fall? After 

 quoting several of the most important opinions, ho stated that, in the hope of 

 finally settling the question, he had commenced collecting all known rain-registers, 

 and had already tabidated more than 6000 years' observations. He proceeded to 

 invite criticism on the mode of discussion which he intended to adopt, and also on 

 a proposed method of delineation, — the rain-fall in 18G0, at 241 stations iu Great 

 Britain, being laid down on a large map as a specimen. 



On some Signs of Clmnges of the Weather. 

 By the Eev. "W. Waiton, M.A., F.B.S., ^c. 

 The author combated nearly all the commonly known rules by which changes of 

 the weather have been anticipated, and gave a few rules which he believed might 

 bo depended upon, chiefly derived from the barometer — especially if the exceptions 

 to the general rules, which he clearly explained, were understood and attended to 

 as they ought to be. 



