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L. An 'Examination of the Review which appeared in 

 the Xril//i Number of The Retrospect," &c., of Doctor 

 Herschel's Essay on the coloured Rings discovered by 

 Sir Isaac Newtox. 



To Mr. Tilloch. 



Sir, jL his paper is transmittefl to you by a little club of 

 friends who occasionally meet tofrethtr for conversing on 

 philosophical subjects, arui who suppose that what is now 

 communicated may be made welcome to a place in your 

 very impartial and vaUuible Magazine. 



For some time past our chief object has been to consider 

 more particularly of the progress of discovery in the diffe- 

 rent branches of physical science, by the increasing ardour 

 for experimental researches, happily now so prevalent both 

 on the continent and in our own country; and which re- 

 flects so nmch lustre on the present times. 



Though our reading is pretty extensive \\\ orisr'mal and 

 other publications of tliis sort both foreign and domeslic, 

 yet it was not till lately we met with some numbers of a 

 periodical work called " The Retrospect,'" &c., which first 

 appeared a few years ago. From the plan of that publica- 

 tion and its high pretensions, as stated in the general title, 

 we had some curiosity to dip into it ; when very soon we 

 found our attention arrested by a review of an experimental 

 essay under the following title : *« Experiments for inves- 

 tigating the Cause of the coloured concentric Rings (dis- 

 covered by Sir Isaac Newton) between two Object-glasses 

 laid unon one another. Bv William Herschel, LL.D., 

 F.R.S." 



When that paper first appeared in the Philosophical 

 Transactions of the Royal Society oF London, we well re- 

 incmber to have perused it with high satisfaction ; not only 

 on account of the remarkable skill discovered by the author, 

 in bringing forward many new and curious experiments 

 leading to important conclusions, but also because vHfe 

 structure of the whole piece appeared to us as an exa!r>ple 

 of the inductive method of proceeding in natural philosophy 

 worthy of ranking with the best models we have of the 

 kind. 



We therefore need scarcely mention our surprise at finding 

 that iioxhinir wlntevcr of that subtile and elaborate pcifor- 

 jnance was held of any account by the writer who furijished 

 that review of it for the 13th Number of The Retrospect. 



Though to those who have studied optics, any vindica- 

 Z 4 tiou 



