TRANSACTIONS OF THE SECTIONS. 
51 
not from a siagle electrical machine, and yet to effect this in one cell, by an ordinary 
idtuc combination, several pairs are required. 
On a 'Property of Alcohol. By Dr. Greene. 
0» the Coloured Glaes employed in glazing the mw Palm House in the 
Hoyal Botanic Garden at Keto. By H. Hunt. 
I( lias been found that plants growing in stove-house# often sufl’er from the scorching 
iiifcHnce of the solar rays, and great expense i* frequently incurred in fixing blinds to 
S etent this destructive calorific influence. From the etiormous size of the new Palm 
»K at Kew, it would be almost impracticable to adopt any system of shades which 
•Wd beeSecUre, this building being 303 feet in length, lOO feet wide, atid 63 feet 
It was therefore thought desirable to ascertain if it would be possible to cut 
wdiese Bcorcliing ray* by the use of a tinted gloss, which should not be objeciionuble 
ahsapDearaaci*, and the question was, at the recommendation of Sic W. Hooker and 
feLindley, submitted by the Commissioner* of Woods and Forest* to Mr. Hunt. 
object was, to select a glass which ahotild not permit these heat rays, which are 
«mo!t active in scorching the leaves of plant*, to permeate it By a series of ex- 
jjfflDienls made with the colou«.'d juice* of the palms themselves, it was ascertained 
the rays which destroyed their colour belonged to a class situated at that end of 
“jriBmaiiu spectrum which exhibited the utmost calorific power, and just beyond 
« limits of the visible red ray. A great mimber of spccirneiu of glass variously 
^ufiictiired were snhinitted to examination, and it was at length asceriained that 
tinted green appeared likely to effect the object desired, 
of me green glnsscs which were e.xamme«i obstructed nearly all the heat rays ; 
W Ibis was not desired; and from their dark colour these were objectionable, as 
the passage of a cwisidcruble (piantity light, which wub essential to the 
•»liliful growth of the plant. Many specimens were manufactured purposely for the 
^iitnents by Messrs. Chance of Bivminghani, according to given directions, and it 
®*inly due to the interest taken by theso gcntleuiL’ii that tb* desideratum has been 
Fvety sample of glass was submitted to three distinct seta of experiment: 
to ascertain, by meosuring off die coioiu-ed ray# of the spectrum, it* trans- 
Jwiicy to luminous influence ; iind, to aacertain the amount of obstruction oflbred 
^ passage of die chemical rays; 3rd, to measure the amount of beat radiation 
"^pemuated each specimen. The chemical chungc* weie tried upon chloride of 
on papers Btwni'd with the green colouring matter of the leaves of the 
. cdorific influence was a«ccrtuino(l by a method employoil by Sir John Ilerschel 
'®qji'rimcntson solar radiations. Tissntepaper stretched on a frame was smoked 
side by holding it over a smoky flame, and tlieti, while the spcctinim was 
^ upon u, the other surface was washetl with strong sulphuric setlier. By the 
of the sihcr, the uoinU of calorific action were most easily obtained, as 
^ dried off in welWefined circles long before the other parto presented any ap- 
of diyness. By these means it wu* not difficult, with care, to ascertam 
c®ditioDs of tlm glass, os to its transparency to light, beat, and cheiiuca 
gj (wtiiil«n). The glaw thus chosen is of a very pale yellow green colour, the 
^ l>cmg given by oxide of copper, and is so transparent Ibat scarcely any fight is 
W/df ’• “’‘“'hilling the spectral rays through it, it is found that the yeliow is 
»^ini,M in iSi;TXL^X red ray is “tTeited in a 
?ree, die lower edge of the ordinary red ray being cut off by it. _ |°, • j 
2? hi* the chemical priiicinle, a# spectral impressions obtained 
K ""* of •liter are the same in extent and character as those procured by the 
Ilii. »i ** •thich have passed ordinary while gla**- . , 
-tb* l^'wever a very remarkable action upon the uon-luminuus heat raj s, 
cidotific rays. It prevents the pemicaliott of all that of 
U|£ h below and ii. the point fixed by Sir Wil mm Herschel, Sir H. 
8**utl(l and Nif t.si._ I,_ 1 1 . .c _/.aUnfi<^ nnCioo. As it 13 
. uEtwm mju (II me UUIIIV u*w .. .~ 
bir John Uerichel as the point of maximum calonflc action. 
