308 I'HILOSOPHICAL TKANSACTIOxVS. [aNNO 17'18. 



knowing when the tin has a proper degree of heat, they might first make an 

 essay with small pieces of the scaled plates, and they would learn from them 

 when the tin is in proper order: but generally speaking, they dip the plates 

 into tin that is more or less hot, according to the thickness they would have 

 the coat to be of. 



Some plates they only give one layer to, and these they plunge into tin that 

 has a less degree of heat, than that into which they plunge those plates which 

 they would have take two layers ; as also when they give these the second 

 layer, they put them into tin that has not so great a degree of heat, as that 

 into which they were put the first time: besides which, it is to be observed, 

 that the tin, which is to give the second coat, ought to be fresh covered 

 with suet, but only with the common sort without preparation; for melted 

 tin is sufficiently disposed to attach itself to solid tin ; and in this case it is 

 to tin itself, to which the new tin is to be joined. 



y4 neiv apparent Motion discovered in the Fixed Stars; its Cause assigned} 

 the Velocity and Equable Motion of Light deduced. By the Rev. James 

 Bradley, Savilian Professor of Astronomy at Oxford, and F. R. S. N° 406, 

 p. 637. 



The observations described in this paper, were first begun conjointly by Mr. 

 Bradley and Mr. Sam. Molyneux, and after the death of the latter, by Mr. B. 

 alone. They were at first begun in hopes of verifying and confirming those 

 that Dr. Hook formerly communicated to the public, which seemed to be 

 attended with circumstances that promised greater exactness in them, than 

 could be expected in any other, that had been made and published on the same 

 account. And as his attempt was what principally gave rise to this, so his 

 method in making the observations was in some measure that which Mr. Mo- 

 lyneux followed : for he made choice of the same star, and his instrument was 

 constructed on nearly the same principles. But if it had not greatly exceeded 

 the doctor's in exactness, we might yet have remained in great uncertainty as 

 to the parallax of the fixed stars. 



This indeed was chiefly owing to Mr. Geo. Graham, to whom the lovers of 

 astronomy are also not a little indebted for several other exact and well- 

 contrived instruments. The necessity of such will scarcely be disputed by 

 those who have had any experience in making astronomical observations ; 

 and the inconsistency to be met with among different authors in their attempts 

 to determine small angles, particularly the annual parallax of the fixed stars, 

 may be a sufficient proof of it to others. Their disagreement indeed in this 



