elevated Rain-gauge, as caused by Wind. 427 



in discussing his observations*, adds the significant remark, 

 " March very anomalous." Now March is in Europe the month 

 in which strong, dry, north-east winds and equinoctial gales 

 most occur, the very circumstances under which we should 

 expect the results to be most erroneous. 



16. I may lastly mention the observations of Dr. Buist, who 

 having made four simultaneous measurements in the Island of 

 Bombay, to determine the fall of rain at different heights below 

 200 feet, reported to the British Association, in 1852, that the 

 results were entirely discordant. Although all proper precautions 

 were takenf, " no satisfactory conclusion could be drawn, because 

 the gauges at the several heights below and at 200 feet did not 

 give uniform results, — sometimes the most elevated gauges 

 having the greatest fall of rain, and at other times the lower. 

 Nor did gauges at similar heights receive the same quantity of 

 rain." 



17. Although the effect of an obstacle upon the wind as 

 causing a separation or approximation of the rain-drops, and 

 a deficiency of rain in an elevated gauge, has now, I believe, for 

 the first time been distinctly brought forward, several writers have 

 made suggestions nearly to the same effect. Thus Howard 

 speaks % of strong winds as robbing the higher gauge. Dr. Trail 

 says§ of Prof. Phillips's observations, "These differences are 

 too considerable to be attributed to anything but some imperfec- 

 tion in the instrument when much exposed to gales of wind ; 

 and it probably arises from eddies being formed round the riin 

 of the funnel, which divert part of the water." 



Again, H. Meikle writes in the ' Annals of Philosophy ||/ "I 

 can hardly pretend to give a complete solution of this well-known 

 paradox, but am disposed to think it is in some way owing to the 

 obstruction which the gauge itself offers to the wind. Perhaps 

 the winds being made to rush with greater rapidity, and a little 

 upward in beginning to pass over the mouth of the gauge, pre- 

 vents the rain from falling into that part of it which is next the 

 wind." 



This almost coincides with my own explanation ; but the 

 remark is confined to the operation of the rain-gauge, which is 

 usually an inconsiderable obstacle compared with the house or 

 tower upon which the gauge is placed. 



p. 359. Those by Bugge at Copenhagen, Mem. de I'Acad. de Copenhagen, 

 nouv. ser. vol. v. p. 227 5 or in Schouw, Climat d'ltalie, p. 131. In 

 Arago's observations February is slightly more deficient than March. 



* Brit. Assoc. Report, 1833, Trans. Sections, p. 408. 



t Brit. Assoc. Report, 1852, Trans, Sections, p. 25. 



J Climate of London, vol. i. p. 104. 



§ Physical Geography (7th ed\), Eacyc. Brit, reprint, p. 184. 



|| Vol. xiv. p. 312, for the year 181!'. 



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