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analyse his sight in the manner herein described, would communi- 

 cate to me the results of his observation on the following points : 



1 . The distance at which the vertical line is seen with the greatest 

 distinctness and best definition. 



2. The distance at which the horizontal line is seen with the greatest 

 distinctness and best definition. Or, 



3. If there be no difference in the distance at which the vertical 

 and horizontal lines are seen with the greatest distinctness and best 

 definition . And, lastly, 



4. Whether or not the observer can satisfy himself that he has 

 the power of adjusting the eye, so as to be able to see the lines with 

 perfect distinctness and definition at any other than one distance. 



N.B. If spectacles are worn, mention the kind of glasses whether 

 convex or concave and their power. 



Note also if there be any difference in the sight of the two eyes. 



II. " On the Light radiated by heated Bodies." By BALFOUE 

 STEWART, Esq., A.M. Communicated by J. P. GASSIOT, 

 Esq. Received February 7, 1860. 



In two papers read before the Royal Society of Edinburgh in the 

 years 1858 and 1859, and published in their Transactions, I have 

 described some experiments on radiant heat, which would seem to 

 involve an extension of Prevost's theory of radiation, known as the 

 theory of exchanges. 



As the paper which I have now the honour to submit to this 

 Society will detail analogous experiments on radiant light, I may 

 be permitted briefly to refer to those points in my previous papers 

 which are thus intimately connected with the present subject. 



In attempting to unfold the logical consequences of Prevost's 

 theory, certain properties of radiant heat present themselves to our 

 view, many of which are capable of experimental verification. 



The following are some of these ; and, for convenience-sake, I 

 shall follow up the statement of each (before proceeding to the next) 

 with a description of the analogous property of radiant light, as in 

 this way the similarity which exists between heat and light will be 

 most readily perceived. 



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