various bodies to the Chemical Rays. 



141 



using the galvanometer at the same time to mark the intensity 

 of hght, try every substance under precisely the same circum- 

 stances. Having completed the exposure of a series, I place 

 all the discs in the mercurial vapour-box together, and the 

 instant the impression appears the strongest, remove them and 

 carefully compare effects. 



The following are the results I have arrived at by these 

 means. At the head of each series I have placed the mean 

 permanent deflection of the galvanometer needle, from ten 

 cai'eful experiments with each of the bodies included within 

 it. By this means a comparative view is given of one series 

 with another. 



Series 1 . — Defection 22° 30". 



Nitrogen 



Atmospheric air 



Oxygen 



Hydrogen 



Carbonic Acid 



Carbonic Oxide 



Steam (invisible) 



Nitrous Oxide 



Water 



Alcohol (absolute) 



^ther (sulphuric) 



Series 2.— Defection 20°. 

 British Plate Glass 

 Iceland Spar 

 Carbonate of Soda 

 Nitrate of Potassa 

 T)\iio, fused and opake 

 Camphor 

 Sulphuric Acid 

 Hydrocyanic Acid(Scheele's) 

 Nitric Acid 



Series 5.— Defection 18° 80". 

 Crown Glass 

 Flint Glass 

 Mica 



French Plate Glass 

 Alum 



Gum Arabic 

 B. Plate and Crown Glass 



German Plate (with a pink 



shade) 

 Two pieces of Crown Glass 

 Purple Fluor Spar 

 Nitrous Acid Gas 

 Iodine Vapour 



Series 4. — Defectioji 17° \5" , 

 B. Plate and Flint Glass 

 Flint and Crown Glass 

 Three pieces of Crown Glass 

 Three laminae of Mica 

 Creosote 

 Oil of Aniseed (German) 



Peppermint (English) 



Rosemary 



Savine 



Four pieces of Crown Glass 



Amber 



Green Fluor Spar 



Oil of Lavender 



Caraways 



Cloves 



Canada Balsam 

 Series 5. — Defection 4° 35''. 

 Green Bottle Glass* 

 Chlorine 



Protoxide of Chlorine 

 Bromine (vapour) 

 — (liquid) 



Lightly-smoked Glass 



* I have been much surprised at some of the manufactunng chemists 

 in London sending out their hydrocyanic acid and other easily decompo- 

 sable preparations in bottles oi 'purple glass, \^ich offers no interruption to 

 the chemical rays. Dark green glass should be substituted, 



