of Sapphire and Diamond. 333 



phire microscopes for the purpose of determining some delicate 

 points in the structure of minerals, in which all our usual re- 

 sources have failed, we hope to be soon able to speak of them 

 from personal observation ; but with such evidence in their fa- 

 vour as that of Dr Goring, Mr Pond, and L)r Wollaston, no 

 farther recommendation is necessary ; and we look forward 

 with sanguine expectation to the discoveries which it will en- 

 able the naturalist to make respecting the structure and func- 

 tions of organic bodies. 



The perseverance and skill of Mr Pritchard in executing 

 lenses of such refractory materials is beyond all praise, and we 

 must make some demand upon the faith of our readers when 

 we inform them that he can execute diamond lenses the one 

 hundredth part of an inch in focal length. Such exertions and 

 such success would, in other countries, have obtained the pa- 

 tronage of sovereigns, and the countenance of government ; 

 but England does not thus honour her scientific artists, and we 

 therefore anxiously hope, that the great merits of Mr Pritchard 

 will not be overlooked by that individual patronage which 

 may still, for a brief period, preserve from exile the declining 

 arts of our country. 



We have been fortunate in obtaining the following list of 

 prices at which Mr Pritchard is able to dispose of his sapphire 

 and diamond lenses : — 



Focal length of sapphire lenses. 

 From 1-lOth to l-30th of an inch, L. % 2s. 

 From l-30th to l-60th of an inch, L. 3, 3s. 

 From l-60th to l-80th of an inch, L. 4, 4s. 

 From l-80th to 1-lOOdth of an inch, L. 5, 5s. 

 Diamond lenses cost from ten to twenty guineas each. 



We are glad to find, that Dr Goring and Mr Pritchard 

 have published the First Number of a Work on the Micro- 

 scope and its Objects, entitled " The Natural History of seve- 

 ral new living objects for the Microscope ^ conjoined with accu- 

 rate descriptions of the Diamond, Sapphire, Aplanatic, and 

 Amician Microscopes, ^c. ^^c." It is to be had of Mr Pritch- 

 ard, 18 Picket Street, Strand, London, and we may perhaps 

 be able to lay before our readers some account of it in a sub- 

 sequent article of this number. 



