Account of the Descent of Mr. Steele's Diving-Bell. 211 



Of the hypotheses that have been proposed to account for 

 the phaenomena in question, that which refers it to an insen- 

 sibility of the retina to certain impressions of light, appears at 

 once the most simple and philosophical. Some eyes, it is well 

 known, are capable of performing the general functions of vi- 

 sion, and are yet unable to perceive those minute impressions 

 of light, which to other eyes are readily perceptible. A retina 

 may be perfectly adapted to receive the due and proper effect 

 of a beam of light, and yet, from some peculiarity in its or- 

 ganization, incapable of perceiving all its component parts. 

 In the present case, the general objects of vision, as relate to 

 form, distance, and magnitude, were perfectly fulfilled, and the 

 sensations arising from white, yellow, gray, and the lighter 

 varieties of blue, appeared in general to be correct; and it 

 would therefore appear probable, that the retina was suffi- 

 ciently sensible to receive correct impressions from pure white, 

 up to colour of a certain intensity; and, beyond which, its 

 power being enfeebled, it communicated only imperfect and 

 confused ideas*. 



In the cases published by Dr.Nicholls, in the Medico-Chi- 

 rurgical Transactions, the anomaly appeared in some measure 

 hereditary; in one instance being derived through the father, 

 and in the other through the mother. In some families this 

 peculiarity of vision appears to be transmitted through a son, 

 without affecting in the smallest degree a daughter ; and in 

 other cases precisely the reverse. In the present instance, 

 however, the anomaly appears to have originated with the in- 

 dividual, no member of his family being similarly circumstanced, 

 — he having always regarded himself as a singular and unfor- 

 tunate exception to the whole. 



Plymouth, July 20, 1823. 



XXXI. Account of the Descent of a Diving-Bell, newly in- 

 vented by T. Steele, Esq. M.A. 



To the Editor of the Philosophical Magazine and Journal. 

 Sir, 

 \ S improvements in physical science at present excite an in- 

 "^"- terest in this country altogether without precedent, and as 

 the great national work the Breakwater in Plymouth Sound, 

 the Pearl Fisheries, the bold enterprise of searching the Spa- 

 nish galleons sunk for more than a century in Vigo-Bay, the 

 search of the Lutine frigate sunk upon the coast of Holland, 



* The point where this change appeared to take place, with respect to 

 blue, was between ultramarine and flax-flower blue, corresponding to 28 

 and 29 of Syme. 



2 D 2 &c. 



