Mr. Talbot on the Nature of Light. 1 1 3 



tuated at the other end of the axis, which it was im- 

 possible to show in the figure. 



(eeeeee). Traversing magnetic needles: two, e'e', revolve 

 in a horizontal plane, the five former in a vertical 

 plane. 



(f). A pendulum, consisting of a magnetic bar suspended by 

 one end, which oscillates as already described. 



(ggg). A mahogany stand or base for supporting the appa- 

 ratus. 



I have some other magneto-electrical facts not generally 

 known, which at a future period I will put on paper, and 

 submit them to your notice ; and should you consider them 

 worthy of attention, probably you will favour them with a 

 place in the Magazine. 



I remain, my dear Sir, yours &c. 

 5 Charing Cross, 10th June 1835. FRANCIS WATK1NS. 



XIII. On the Nature of Light. By H. F. Talbot, Esq., F.R.S.* 



J 1. AN attentive consideration of the modern discoveries 

 ^*- in optics leads to certain views concerning the na- 

 ture of light, very different from those that are commonly en- 

 tertained of it by persons who have not reflected on the sub- 

 ject. 



If we admit the truth of the undulatory hypothesis, it fol- 

 lows as a necessary consequence that light (or rather the 

 aetherial medium whose vibrations constitute light,) is present 

 everywhere, and at all times, ready to transmit in any direc- 

 tion, and to any distance, whatever vibration may be excited 

 among its molecules. It is therefore as truly and actually 

 present with us during the darkest night, as it is in the day- 

 time, or even in the sunshine. This is a difficulty, and a kind 

 of paradox, from which the doctrine of emission is free. 



As, however, many other things have been found to be true 

 which are exceedingly contrary to the first impressions of our 

 senses, (for instance, the earths motion,) there is no reason for 

 rejecting this hypothesis d priori, if it explains other facts in 

 a satisfactory manner. 



It is remarkable that intense light is sometimes produced 

 under circumstances where there does not appear to exist any 

 adequate cause for its production. Every one knows the ef- 

 fect of placing a bit of lime in the oxyhydrogen flame ; but, 

 I believe, no satisfactory explanation has been given of it. It 

 has been attributed to the formation and subsequent combus- 



* Communicated bv the Author. 

 Third Series. Vol.7. No. 38. Aug. 1835. Q 



