20 
REPORT—1847. 
acid, a process the opposite of that which takes place when chlorophyl is 
produced. This change is required in order that the amylaceous principle 
in the seed may be rendered sufficiently soluble for the support of the prm, 
previous to its being able to obtain the requisite nutriment from the soilj sa 
that, if the decomposition of carbonic acid be owing to the yellow ray, this 
same ray ought to be tlie last to produce any effect on the gtTinination of seeds. 
As it is however possible that some source of error may exist in my exp^ 
riments, I shall distinctly state every form of apparatus employed by me, and 
the actual conditions of tlu; solar radiation* under which the diflerent results 
were obtained. 
In the first place I shall record my experimetits on germination. 
It became important to d«^termine if any (jfffCt was produced by white 
light. For the purpose of ascertaining this a quantity of common cress (Lf‘ 
pulium satmini) and turnip-scoil (^lirassica 7inpHs) was placed upon raoL'l 
earth and very lightly covered with fine saml; one half was screened iVom the 
light by a blackened board, and the other fn'idy exposed. Under the shaded 
lidt the germination was between two and ihreo days in advance of de 
exposed portion. 
This experiment was rejK’ateii, using a glass trough containing a weak di¬ 
lution of bicht'omute of potash half an inch in thickness over the illumiDated 
portion. This solution admitted tlm permeation of 87 jiart* of the luiuiiio^ 
rays, 92 of the calorific r.ayi’, and 27 of the chemical ray*. The object in 
this instance was to ascertain if any greater rotnrdation was produced hythe 
luminous rays, from which the chemical principh? was to a eonsiderable extent 
removed, than by imro white light, M-hich it will be borne in mind I prupi*® 
to regard as a compound of 100 [mrts of each, light, heat and actliiistn. The 
result was that the seed under the influence of this yellow niediuiiididnot 
germinate until five days after the seeds in the <lark. part of the box. 
Upon substituting a solution of sulphate of cbruuuum and potash which 
admitted the permeation of 85 parts of light, 92 parts of heat, and only 7 of 
actinism, the germination was prevented entirely in four experiments 5 and in 
the fifth, days after the seeds in the dark had gennmaled, half a down 
ot seeds of cress showcil symptoms of germination. These cxpcrimoiits were 
many trniw repeated and iiUvays with sinfilar results. W'a have thus satis- 
metory evidence that light deprived of tlic principle or power of chemical 
^'f’thc plant, by preventing the vitality of the 
germ from manifesting itaolf. ® 
bin'^iSirnf g^'-ndtiation is the process of chemical com- 
cnciiiff tldfs fhn “xygfh and hydrogen, yet the power in^u* 
snmlf . character, though cvideiitlv dependent on 
profluciim'^thl*?^^'^^*""' " ^ light,Ir the principle 
mbilrd^ fear If 
rai' SuceTunvT''^'^\-‘” principlcof the solar 
aXx rropSl in procL. i ith this vie*, 
by an under layer r ' 'n® aad this was kept wrf 
the light, and the othorY di’ completely screened fr^ 
dosirablo to try bifluence which it was thought 
glasstjs, mid by LSb'nrof" uS interposition of a series of blU'^ 
Tile tested class admlHir. 1 .? of copper, or amnioniate of copper- 
actinism 90 parts. permeation of—light 40, heat 72, 
