568 



showed, that the mean velocity for any tune cannot l^e con- 

 cluded from the mean pressm-e, even when the relation between 

 them is known. However, space measm'es were not entirely 

 neglected. LomonosofF, in 1749, contrived one which, by an 

 ingenious arrangement, recorded the quantities of wind that 

 blow fi'om'each point, INIi*. Richard Lovell Edgeworth made 

 one in 1 783, which, though invented for another purpose, was 

 used as an anemometer. It was a set of windmill vanes, re- 

 volving once for each foot of wind, and the tm-ns reckoned by 

 that beautifid contrivance now called the Cotton Counter, the 

 invention of which is attributed by Willis to Dr. WoUaston. 

 Dr. Wollaston, however, had seen this very instrument, of 

 which he exhibited the fragments. It was made to measure 

 the ascent of a balloon, and was used for this purpose by our 

 countryman Crosby, in liis perilous adventm-es in 1785, being 

 saved by him in the sea. Woltman's hydrometric fly was pro- 

 posed by him in 1790 ; but the person who first perceived the 

 fidl advantages of this measure as an integi'al instead of a 

 differential, and established its superiority in public estima- 

 tion, was Dr. Whewell. This instrument, which was shown 

 in Dubhn to the British Association in 1835, recorded space 

 and direction. It was used by many here — by Captain Lar- 

 com, but above all by that accomplished observer, Su'W. 

 Snow Harris. He, in a most striking communication, in 1842, 

 to the body just mentioned, gave his result, and at the same 

 time pointed out some defects in the instrmnent, which led Dr. 

 Robinson to turn his attention to the subject. In the follomng 

 year he constructed the principal parts of the new anemo- 

 meter, and has ever since been engaged in impro\Tng it. The 

 principles which guided him were: 



First. It shoidd be so powerful, that friction can only 

 slightly retard it. 



Second. So large that it may include in its range a large 

 assortment of aerial filaments, and thus give an average mea- 

 sure. 



