before the Botanical Congress in London. 235 
the effect of the different visible or invisible rays which enter 
into the composition of sunlight. For the sake of exactness 
nothing is superior to the deci piaiilar of the ]uminous rays 
by a prism, and the fixing the rays by means of a heliostat. 
co 
periments concerning the action of various rays upon the pro- 
duction of oxygen by leaves on — the ge of the green 
coloring matter, have only confirmed the discoveries made in 
1836, without either prism or reimens by Professor Daubeny,’ 
from which it appears that the most ‘luminous rays have the 
ost Panes me to them the hottest rays, and lastly those 
balled chem 
Dr, Gardade) in 1843, Mr. Draper singin after, and Dr, 
C. M. Guillemin in 1857, * Gorroborated by means of the prism 
and the heliostat the discovery of Dr. Daubeny, which negatived 
the opinions prevalent since the time of Senebi ery Tessier, 
and which were the result of erroneous” experiments. It wa as 
difficult ~ believe that the most refrangible sneak for in- 
stance, which acts the most on metallic gare in age? 
*, Dauben Philos, Trans., 1836, 
OE. - cuss Band P iL Migs 18H extract in French in La Lop Res 
; Dra 
Fe r, Edinb. Phil. ~~ gy “aa 1844, 
ih: _ 1844, L li fe ©. M.), Ann. Sci. ie stond ser. 4, vo 
vo Me oui en hk he p- 69; Tessi m. Acad. Sci., 17883 ‘Gilby, 
i. de Chimie, 183, va Succo w, Co rmintatie: “is ar effectibus chemicis, in : 
4to, Jena 1828, a Zantedonehi. ‘cited by Dutrochet, Compt. Rend. Acad, Sci, 
1844, oye se : 
* Asa proof o he persistence of the old age 7 will quote a phrase of Pro- 
fessor Tynall’s, . his most clear “On Radiation,” (London, 
1865,) p. 6:—“In the nee of their houtal pire thea sate? violet gr dips 
of the utmost i the organic world.” Ido not know whether the au- 
thor had in view an influence of the chemical rays over the ani Ais - 
according to ce passages ~ Mr. Sachs, I doubt if they have more — over 
eee sat ppeared inthe Tomiie! hey 
are collected and yan inenter markable volume called Handbuch der -hysit 
logischen Botanik, vol. iv, lie. 1868, pp. 1 to 46, 
