584 PHILOSOPHICAL TRANSACTIONS. [aNNO 1682-3. 



tion, to show that not only the whole circumference of the wing, as here 17, 

 is beset with great and small feathers, as fig. 18: but also the nerves that stiffen 

 the wing. The film of the wing which is between the nerves, seems by the 

 microscope to be full of a great many small risings ; but upon a stricter exami- 

 nation, they are really small hairs, as fig. 19, where a beginning was made to 

 represent the whole wing : ABC are the feathers, and A DEC are the hairs on 

 the film. 



A certain physician having told me that several people afflicted with agues, 

 had been cured by the use of sal volatile oleosum, which had attenuated and 

 rarefied their blood. I resolved to make what observations I could of the mix- 

 ture of that salt with blood. And therefore pricking my finger with a needle, 

 I put the first time two parts of blood to one of salt ; a second time equal parts 

 of each : the blood turned immediately of a more lively red colour, as blood 

 usually does when mixed with fair water. 



The parts of that blood that lay nearest the salt, changed colour first, and 

 by degrees those further distant. But taking my microscope to observe it, I 

 found the blood globules each to be dissolved into 6 distinct globules. 



I then took four parts of salt, &c. and one of blood, and viewing it as quick 

 as I could with my glass, I found some of the blood globules much diminished 

 in -i- of a minute, but in -|- of a minute they were wholly dissolved. I saw once 

 20 blood globules at a distance from the rest; but in continuing to count them, 

 they came first to 18, then 16, after to 3 or 2, which also were dissolving. — 

 There was also here and there a globule that would not dissolve; nor with a 

 very little salt would any. 



A Correction of the ITheory of the Motion of the 4th Satellite of Saturn. By 

 Mr. Edmund Halley. N° 145, p. 82. 



I here send you an astronomical account of the most remote of all the planets 

 of our vortex, and of the satellite of Saturn, discovered in the year l655 by M. 

 Huygens, who in that accurate treatise of his, Systema Saturnium, from page 

 25 to 34, gives the theory of its motion, as well as the shortness of the interval 

 of time between his observations would admit. 



The late conjunctions of Jupiter and Saturn giving me frequent occasions of 

 viewing them both, with a telescope that I have of about 24 feet, and pretty 

 good of that length, I easily remarked this satellite of Saturn, and having found 

 it in a convenient position to determine its place, I perceived that Huygens's 

 numbers were considerably run out, and about 15 degrees in 20 years too swift; 

 this made me resolve more nicely to inquire into its period ; and accordingly I 



