On representing by Diagrams the Uesidts of Observations. J 27 



quantities, taking care that the sum ol the arbitrary quantities 

 shall vanish; or we may change the right-luind side of (10.) 

 intp X (^0» X '^^'"g ^^ arbitrary function. ,, _ ,, , y 



"'4. The values of a to be selected in the tra,nsforrnations of 

 duadratics and biquadratics, which I cave at p. 384 of the'last 

 volume of this work, are, respectively, 1 and —1. 

 ^ ^dambridge, July 1, 1845. t^ = (or) oi^ 



XXI. On a certain Method of fepresenting by Diagrams the 

 \ 'Mesults of Observations. By the Rev. S. Earnshaw, M.A.f 

 Cambridge'^. 



IN attending the proceedings of the Physical Section of the 

 British Association at the late meeting in this place, I 

 was struck on more than one occasion with a defect in the 

 method which had been employed by some of the experimen- 

 talists in representing their results on paper. My remarks 

 refer to those cases in which polar co-ordinates were used, as 

 was done in two very interesting and important papers ; one 

 "On the quantity of rain which had fallen with different 

 winds at Toomavara," and the other " On Shooting Stars.." 

 In the former paper, the observer (the Rev. Thomas Kno^) 

 reduced his observations to a pictorial state, by drawing upo4 

 paper from a fixed point several lines to represent as many 

 directions of the wind ; and this done, he set off upon each of 

 these lines, measuring from the fixed point, a length propor- 

 tional to the quantity of rain which had fallen while the winp 

 was in that particular direction, and within certain limits on 

 each side of it. Perhaps this will be plainer by a figure. 



From O draw eight lines, ma- ^^ 



king angles of'iS^ with each other, ii« uj iow ?a Jyjljdo lijo uadi 

 to represent the directions of the no i%^iJnBiJji Jfldi av^oj 

 wind according to the letters 3'>ab9'r\j^1u|^ ^J^gnJ'd 

 placed at their extremities. From 

 O set off OB to represent the wii+*- 

 quantity of rain which fell, not 



only when the wind was in the ^ .,^ ^^,^^,^^^^^^^^ 

 north but also when it was m .^^[nu^JmB^^s^od^ 

 any direction between the points ^^ ^ i«?^ „„ .,„„ „. ^'. 



N.N.E. and N.N.W. On a si- - j -^ ,,5^,^^^.^ m-,^„„;5 

 milar plan set off the other portions' 6C,'0D, ... . This was 

 the method employed by Mr. Knox ; and a similar principle, I 

 believe, was made use of by M. Gravierf in reducing to paper 



* Communicated by the Author. 



t A notice of M. Gravier's researches on Shooting Stars will be found 

 among the miscellaneous articles of the present Number.— Ed. 



