188 Some Remarks upon an urinary Calculus 



place 1 opposite to 64 ; and against the divisor 2 will stand the 

 quotient 32. Given 4, 8_, and S, to find a fourth proportional : — 

 place 8 opposite to 8 ; against 4 is found 16. To find the fac- 

 tors of 64 : — bring 1 to that number ; in this position of the scale 

 every factor will be found opposite to its reciprocal ; as 2 against 

 32j 4 against 16, 8 against 8, which is consequently the square 

 root of the given number. Or, if the factors of 640 be required, 

 the same position of the slide shows that 2x320, 4x160, 

 r. X 128, 8x80, 10x64, 16x40, and 20x32, equally produce 

 that number; whilst the juxtaposition of 25-3 in both lines 

 shows that to be its root with as much accuracy as can be ex- 

 pected from so short a radius. 



The scale reduced in length in the manner above described, 

 but without the inversion of either of its lines, is competent to the 

 solution of all questions of simple multiplication or division ; and 

 in this form it is prepared for the use of the officers of the Ex- 

 cise by R. B. Bate, of the Poultry, the accuracy and neatness of 

 whose workmanship 1 cannot avoid mentioning, though I am 

 sensible they are too well known to derive any publicity from this 

 notice of them. 



Feb. 8, 1817. SlLVANUS BeVAN. 



XLVII. Some Remarks upon an itrinary Calculus havins a Cinder 

 as its Nucleus; with a Notice of other Calculi containing a 

 small Quantity of Carbonate of Lime. The occurrence also 

 of Brown Spar, noticed in the Trap Rock near Newport in 

 Gloucestershire. 



j-j- To Mr. Tilloch. 



Sir, — XIaving seen in one of your late numbers an account 

 of an urinary calculus chiefly composed of carbonate of lime, I 

 have been induced to send you the following particulars of a cal- 

 culus composed likewise of carbonate of lime, and further inter- 

 esting from the substance forming its nucleus. 



This substance is a common cinder, and it constitutes the 

 greater part ;.f the specimen. Although it is impossible to mis- 

 take its appearance, I may observe that sulph. acid when treated 

 with a very small quantity of it very soon acquired a dark-brown 

 colour. The niuder is surrounded but not intermixed with a 

 layer of a yellowish-white colour, which dissolves in muriatic 

 acid with a brisk effervescence, leaving behind a few tender floc- 

 culi. The solution being treated with subcarbonate of potash 

 yielded carbonate of lime nearly to the amount of the original 

 quantity employed ; viz. two grains. To certify the presence of 

 carbonic acid, I put a very small quantity of the calculus in a 

 ■two-dram bottle, which immediately upon being filled with a di- 

 lute 



