Prof. Tyndall's Contributions to Molecular Physics. 527 



The change of quality produced in the radiation by the intro- 

 duction of a platinum spiral into a hydrogen-flame is illustrated 

 by a series of experiments, executed for me by my assistant, 

 Mr. Barrett, and inserted subsequently to the presentation of 

 this memoir. 



Table XXXIX. a.- 

 1. Hydrogen-flame; 



—Radiation through Liquids. Sources : 

 2. Hydrogen-flame and platinum spiral. 







Transmission. 



A 







Thickness of liquid 



Thickness of liquic 





0-04 inch. 



0'07 inch. 



• 



Flame 



Flame and 



Flame 



Flame and 



Name of liquid. 



only. 



spiral. 



only. 



spiral. 



Bisulphide of carbon 



77-7 



87-2 



70-4 



86-0 



Chloroform . . . 



54-0 



72'8 



50-7 



69-0 



Iodide of methyle 



31-6 



42-4 



26-2 



36-2 



Iodide of ethyle . . 



30-3 



36-8 



24-2 



32-6 



Benzole .... 



24-1 



32-6 



17-9 



28-8 



Amylene .... 



. 14-9 



25-8 



12-4 



24-3 



Sulphuric ether . . 



13-1 



22-6 



8-1 



22-0 



Acetic ether . . . 



10-1 



18-3 



&6 



18-5 



Alcohol .... 



9-4 



14-7 



5-8 



12-3 



Water 



32 



7-5 



2-0 



6-4 



Here the introduction of the platinum spiral changed the 

 periods of the flame into others more in discord with the periods 

 of the liquid-molecules, and hence the more copious transmission 

 when the spiral was employed. It will be seen that a transmis- 

 sion of 2 per cent, is here obtained through a layer of water 

 0*07 of an inch in thickness. 



Another series of experiments, also executed by my assistant, 

 gave the following results of the radiation of a hydrogen-flame 

 through layers of water of five different thicknesses : — 



Radiation through Water. 



Source, hydrogen-flame. 

 Thickness of liquid. 



0-02 

 inch. 

 5-8 



0-04 

 inch. 



2-8 



0-07 

 inch. 

 1*1 



0-14 0-27 

 inch. inch. 

 0-5 0-0 



Transmission per 100 

 Wishing to compare the radiation from a flame of ordinary 



ously inferred, from the paucity of luminous and extra-violet rays in the 

 hydrogen-flame, that its periods must be extra-red. And he deduced from 

 this that the heating of a platinum wire in a hydrogen-flame must consist 

 of a change of period. A very interesting communication from Dr. Akin 

 on this and kindred subjects will be found in the ' Reader* for the 26th 

 of September 1863.— April 5th, 1864. 



