24^2 



REMARKABLE STRATA OF FLINT. 



perifcopic glafs -glafs, I cannot without pain read quite twenty-four linef?; but 

 * upon fubftituting the perifcopic glafs fixed in the fame pofition, 

 I can with exfe difcern every word in the page, which contains 

 forty lines. 



—or rather as The enlargement of the field of view obfervable in this trial 

 is futficient to evince the fuperior utility of the perifcopic glafs ; 

 but were there occafion to compare more nearly the circular 

 areas that may be fe^n with equal diftinclnefs, they would be 

 found to differ by a ratio as great as that of three to one. 



A correfponding This dilFerence is of courfe more evident in glaflTes of fo high 



flialJovve^^lcnfes. po^^r than in thofe generally ufed by long-fighted perfons for 

 common purpofes; but it cannot be doubted, that a corre- 

 fponding, though fmaller, inequality fubfifts wherever there is 

 the fame diflimilarity of conftrudion, even when the focal dif- 

 tance is longeft. 



ponclufion. The advantage in queftion is therefore indifpirtably proved 



by dired experiment; to the notelty of it Mr. J. himfelf has 

 unintentionally contributed very fatisfaftory evidence ; but as 

 to its importance, thofe alone, who have the misfortune to la- 

 bour under any defedl of vifion, muft ultimately decide. 

 I remain. Sir, 

 • . Your obliged humble fervant, 



Mardi 20, 1804-. W. H. WOLL ASTON. 



IL 



AddUional Ohftrtations onfome remarkable Strata of Flint in tht 

 Jjle of Wight, in a Letter from Sir Charles Englefield, 

 Bfirt. F. R. S. /o John Latham, M. D, F. R. S. andL. S* 

 (See Page 183 o/ the prefent Number,) 



Dear Sir, 



Obfcrvations on 1 FEEL much flattered at the notice taken -of my Paper on 

 remarkable ' ^ijg ^.h^jj; pjts in the Ille of Wight by the Linnean Society ; 

 ftrata of flint in , , .^ , , ? r .l • 



the Ifle of ^"^ ^^ i wiln to render my account or the very curious appear- 



Wight. ances obferved by me in them as perfe6l as I can, the follow- 



ing additional obfervations on the fubjedl made during a fecond 

 vifit laft year are, by your favour, fubmitted to the Society. 



» Linnean Tranfa^lions, Vol, VI, 



Tlie 



