MEMOIR ON COLOURED SHADOWS. 23 



made in this paper, and indeed from what may be feen in Jnftru£lions fot 

 every part of the kingdom, in the charader and appearance <="'^ivating the 

 of oaks growing without cultivation, itfeems afcertained, that 

 ** acorns fet with the fpade or dibble, without digging or 

 '' tillage," can never be depended on to form good timber ; 

 and even in the moft favourable circumftances of this cafe, the 

 growth will be exceedingly flow and precarious. The fame 

 may be faid of " young plants, previoufly raifed in nurferies, 

 " and tranfplanted ;" for if the tap-root be cut, broken, or 

 in any degree injured, which in tranfplanting it is almoft im- 

 poffible to avoid, that plant will feldom become a vigorous 

 and flouriQiing tree. To form a courfe of experiments on fuch 

 a plant as the oak, is not a^'cry eafy matter. To fulfil expli- 

 citly the conditions of the Society would require a great length 

 of time, and would be attended with confiderable expenfe, 

 from which future candidates may in a great meafure be exo- 

 nerated. Theraifing even one acre in the manner here afcer- 

 tained might be prod u dive of great pecuniary advantage, if 

 the fafts and experience detailed in this paper are permitted 

 to prove the inutility of the other two methods, and confe- 

 quently to remove the neceffity of employing fo much ground 

 upon them, at an expenfe they will never repay, 



Chelfea College, Nov. 4f, 1801. 



IV. 



A Firjl Memoir on coloured Shadows, 

 ByCit. J. H. Hassenfratz. 



(Concluded from Vol. VI, page 285.; 



PART THE SECOND. 



JL HOUGH the (hadow produced by the concurrence of the shadows pro- 

 folar light with that of theatmofphere, ufually prefents only that ^^^^Z lights, 

 feries of colours contained in the portion of the fpe6lrum, arc more various 

 between green and violet, it is not the fame with the co- j^gj^^^^fg^^e^ 

 loured thadows obferved in the interior of rooms, when fe- f^re defcribed. 

 veral lights dire6l or refleded concur with that of the at- 

 raofphere to enlighten the plane on which the fhadow is 



obferved 



