732 PHILOSOPHICAL TRANSACTIONS. [aNNOI 672. 



proaches to scarlet. And perhaps some of these liquors mixed together, whose 

 tinging parts do not coalesce, will become more opaque. But I am not solicit- 

 ous about the event, both as the experiment is clearer in liquors apart, and as 

 the experiment (like the phaenomena of the iris, and the tincture of lignum 

 nephriticum, and of other natural bodies) I proposed not to prove but only to 

 illustrate the doctpne. 



I do not take it amiss that the Rev. Father calls my theory an hypothesis, 

 inasmuch as he was not acquainted with it. But my design was quite different, 

 for it seems to contain only certain properties of light, which now discovered I 

 think easy to be proved, and which if I had not considered them as true, I 

 would rather have them rejected as vain and empty speculation, than acknow- 

 ledged even as an hypothesis. 



Two Observations about Stones found, the one in the Bladder of a Dog, 

 the other fastened to the Bachbone of a Horse: both mentioned in 

 two Roman Journals de Letter ati. N° 84, />. 4094. 



The dog was a pretty spaniel, two palms and a half high, white, and an 

 excellent setter for quails. Being kept tied, as such dogs are wont to be, he 

 would rather have burst, than urine or dung in the place where he was kept. 

 By reason of his aptness to bite, he was cut when he was five years old, and 

 two years after that, he began to urine with much difficulty. And as often as 

 he was loose, he ran immediately into the garden, and eat pellitory of the wall, 

 and fig-leaves. This disease continued with him for five years together, some- 

 times with that violence that his master had him syringed, and anointed with 

 oil of scorpions, and used other remedies to help the poor creature. 



At length he died at twelve years of age, and being opened by a skilful ana- 

 tomist, there was found in his bladder a stone weighing an ounce, of an irre- 

 gular figure, white, yet here and there with some reddish specks ; and in the 

 bottom of the bladder was found much small white gravel, and in the mouth of 

 the urinal passage a stone as large as a great pine-kernel, white and tender. 

 The rest of the body was all swelled. 



The other stone, that was fastened to the backbone of a Spanish gelding, 

 that died at the age of between thirteen and fourteen years, weighed four 

 ounces and a half; it was round and a little flatted; of an olive colour, marked 

 with red specks, like coagulated blood ; and so polished and shining, that it 

 reflected images. It was wrapped up in a membrane full of fat, and fastened on 

 both ends to the backbone, over against the kidneys. 



