404 Scientific Intelligence. 
thermal values CO,O = 68,000, H 2,0 =68,000, C®H!? O&= 
642,000, 1 cub. centim. of CO? decomposed as in (i would require 
ramme-units of heat, or its mma srg alent, whereas the 
complete change into grape sugar of the same amount of carbonic 
acid requires only 4°78 gramme un ie "But , we ate seen before, 
1 square decimetre of green leaf functions at "the rate of 5°28 cub. 
centims. of carbonic acid Paiiailat ed per hour; therefore 5°28 + 
4°78 — 25-23 represents the number of gramme-heat-units con- 
served through the absorption of light in the above period of time. 
Pouillet estimates the mean total solar radiation per square 
decimetre exposed normally to the sun’s rays in or near Paris, per 
our, as 6,000 gramme-units, so that 6,000 — 25:23 = ats repre- 
sents the fraction of the entire energy conserved. The estimate is 
by no means too great, as Boussingault has shown the leaf may 
function at twice the above rate for a limited ames and as both 
sides of the leaf are included in the measurement of the green 
surface in his memoir, we ought to double the es for a leaf 
exposed perpendicularly to the sun’s rays, increasing the above 
as ig ig 3 120th art. 
nee has a strong absorptive action on the rays of light of low 
eee G just those rays that are in part selected by chloro- 
phyl), bic the well wn a lines of the we 
spectrum. 8 esence, refore, of varying quantities 
aqueous Vv epee in t pote cma in a atpodalod produces a con- 
siderable difference of rate in the osition ae iB the 
d 
pom sition. Thus the same plant in different ee con- 
ditions may gaboriie different substances. 
n the Law of Extraordinary a in Iceland he 
by a. G. soca M.A., Sec. R.S. (Proce. Roy. Soc.)—It 1s pee 
—— years since I carried out, in the case of Iceland ised 
met of examination of the law of refraction which I desert 
admit of scrutiny, across the two acute angles, in Pade of ore 
wave-normal within the crystal oe ig respectively iné india as 
of 90° and 45° to the axis. The he cut fa the 
referred by Thode to ‘to thé clea oe Pinkie and thereby t° 
axis. The =_ observed was the bright D of a soda-flame. 
