204 On the Priority of Invention of f,he Safe-lamp. 



over the retina. A small portion of them would therefore fall 

 on the circular base of the optic, verve; and the few rays that 

 might fall on it could produce neither erect nor distinct images. 



Had we not been assured hy Mr. Horn that his " Theory of 

 Vision is .sinictwned ly /li^/i philosophical authority," and did 

 I not find it copied, witli approbation, into Hntton's Mathe- 

 matical Dictionary, I should deem some apology necessary for 

 ihiii occupying a page of your valuable Magazine. 

 1 am, sir. 



Your very obedient servant, 

 March 10, 1817. L. S, 



P. S. Page 93 of his pamphlet, Mr. Horn tells us, that if a 

 convex lens be fixed in an aperture of a window-shutter in a 

 dark room, and the eye placed in its focus of parallel rays, " no 

 image whatever impresses the organ ; a circular spot only is 

 perceived, uniformly tinged with the prevailing colour of the 

 landscape." This none will doubt. But without referring to his 

 pamphlet, it will not easily be credited that he attributes the 

 absence of images in this case to the pencils of rays proceeding 

 from the objects of the landscape having their foci on the re- 

 tina! On this principle (with no little exultation at its disco- 

 very) he accounts for the apparent insensibility of the optic 

 nerve, which, according to him, only happens when the pencils 

 of rays proceeding from the pupil have their foci on its base ! 

 Surely, if Mr. Horn could for a moment divest iiis recollection 

 of his imaginary discoveries, he would, like others, perceive that 

 in such a position as he has descriljed the eye with respect to 

 the lens, the pencils of rays prjoceeding from the objects of the 

 landscape could not possibly have their foci on the retina. 



LH. Letter from Mr. G. Stephknson of the KiUingivorth 

 Colliery: ivith a few Remarks on his Claim to Priority in the 

 Invention of the Safe-lamp, by the Editor. 



To Mr. Tillock. 



Sir, — 1 OBSERVE you have thought proper to insert in the 

 last number of the Philosophical Magazine, your opinion that 

 my attempts at safety-tubes and apertures were borrowed from 

 what I had heard of Sir Humphry Davy's researches. You can- 

 not have read the statements I considered myself called upon to 

 lay before the public, or vou would not thus have questioned my 

 veracity without producing the evidence that induced you to do 

 so. If fire-damp was admitted to the flame of a lamp through 

 a small tube, that it would be consumed by combustion, and that 



explosion 



