66 LETTERS ON SCIENTIFIC SUBJECTS. 



holds. We desire, therefore, you would at your leysure in- 

 struct us farther in the demonstrations of all the cases re- 

 mayning, which I suppose you can easily and soone doe out 

 of the severall figures in the English paper. We long to 

 heare fro you and to receive those things you promised. My 

 Lord would gladly be a partaker of, and a student in your 

 philosophicall discourses, if you would impart them to him. 

 He is much taken with the device of your perspective glasse 

 and desires you would calculate a line for it, at a good propor- 

 tion, as 40 to one, that we might see whether it would hold 

 good in practise as well as it seems in speculation ; and if it 

 doe, he will be ready to further you in any way you shall 

 desire. Both his Lordship and Sir Charles recommend their 

 love to you and soe does 



Your friend to serve you, 



ROBERT PAYNE. 



SIR CHARLES CAVENDISH TO WALTER 

 WARNER. 



[MS. Birch, Brit. Mus. 4405, fol. 161, Orig.] 



Welbeck, May 2nd, 1636. 



Worthie Sir, Though I have had some diversions, yet I aske 

 your pardon that I have bin so longe before I returned you 

 thankes for the two tracts you were pleased to send me ; I 

 give you manie thankes for them, and esteem (as they justlie 

 deserve) verie greatlie of them. I received latelie a letter 

 from Mr. Hobbes, where amongst other things he sent me 

 this paper heer inclosed, which is an experiment of the place 

 of the image of a thing contrarie to the olde tenet ; a candle 

 being put into a glasse of a cylindricall forme, the image hangs 

 perpendicularlie over the candle itself, as is expressed in this 

 figure, and not at the concourse of the perpendicular from the 

 object with the visuall line which in this figure is at the point 

 A. Mr. Hobbs conjectures that the approach of the image 

 proceeds from the strength of action from the object, which 

 is greater heere than in a plaine, by reason of the concavitie 

 of the cylinder which gathers the beames, and by that meanes 

 makes the motion or streame of the reflected beames stronger. 

 I desire at your convenient leasure to have your opinion of it, 

 as also of this place of the image in convex glasses. I have 



