422 APPENDIX II. 



between its folds or on the pins, and to the other end a 

 small weight, serving to draw the tape tight through a 

 hole in the blackened card. I enclose you the whole 

 apparatus arranged in this manner, together with a few 

 fibres of the Vigonia wool, which exhibit the colours in 

 great perfection, constantly giving 14^ as the characteristic 

 number. The directions for the use of the instrument 

 might be engraved and printed on the card if it were 

 thought desirable. 



I also take the liberty of forwarding to you a letter 

 which I have just received from a French gentleman, who 

 claims the protection of the Royal Society. You will best 

 judge whether the case requires or admits any exertion of 

 your well-known liberality and kindness. 



Believe me, dear Sir, with the highest respect and 

 esteem, your faithful and obedient Servant. 



DR. THOMAS YOUNG TO SIR JOSEPH BANKS. 



Worthing, October 6, 1810. 



MY PEAK SIR, I shall be most happy in assisting you to 

 form a judgment from your own observation of the utility 

 of my little instrument ; but I cannot forbear to trouble 

 you with a few specimens of wool, which I imagine will 

 exhibit the appearances so obviously as at least to convince 

 you of the perfect practicability of the method. You will 

 observe, by merely looking through them at a candle, that 

 there is a manifest difference in the size of the rings, and if 

 the colours are not sufficiently conspicuous when the card 

 is used, the central hole may be made a little larger with a 

 bodkin ; and a common pair of spectacles, such as you 

 would use in mending a pen, will be amply sufficient for 

 remedying the flatness of the eye. 



I do not apprehend that the different magnitude of the 

 different fibres of the same fleeces is any objection to the 



