54 PHILOSOPHICAL TRANSACTIONS. [aNNO 1673. 



of Oct. 167 1 , SO that in about 480 days it made a certain number of entire revo- 

 lutions, which can be no more than 7 ; since each of them is doubtless of more 

 than 68 days. If we count 7 of them, each would be 68-1- days : if we count 6, 

 each would be 80 days; if we count but 5, each would be 96 days. But this 

 last supposition can by no means be made to agree with the two observations of 

 Dec. 1672, and the first does not agree with them so well as the second. The 

 proportion of the apparent distances in the observations of Feb. which are the 

 best, would make us estimate each of its revolutions between 80 and 96 days ; 

 but the proportion of the greatest digression of 1671, compared with that of 

 the two other satellites, together with their periods, agrees better with 80 days.* 

 Therefore in the Ephemeris which we give of one revolution, we follow this, 

 until we get a more precise determination, which requires a greater number of 

 observations. 



Extract of a Letter of David von der Beche, a German Philosopher and Physician 

 at Minden, concerning the Principles and Causes of the Volatilization of Salt of 

 Tartar and other Fixed Salts. Printed at Hamburgh, 1672. N° 92, 

 p. 5185. 



By the volatilization of salt of tartar, is here meant the volatilization of the 

 tartareous acid from cream of tartar, (crystals of tartar, acidulous tartrite of pot- 

 ash) . It is unnecessary to notice any farther concerning this uninstructive che- 

 mical paper. 



Observations on the Nature of Snotu. By Dr. Greiv. N° 92, p. 51 93. 



If Aristotle and Descartes, he. who have written of meteors, and amongst 

 them of snow, have not yet given a full account of it; it will not be needless to 

 inquire further of it. He that will do this, will do it best, not by the pursuit of his 

 fancy in a chair, but with his eyes abroad; where if we use them well fixed, and with 

 caution, and this in a thin, calm, and still snow, we may by degrees observe: 1st, 

 with M. Descartes and Mr. Hook, that many parts of snow are of a regular figure ; 

 for the most part, as it were, so many little rowels or stars of 6 points ; being 

 perfect and transparent ice, as any we see on a pool or vessel of water. On each 

 of these 6 points are set other collateral points, and those always at the same 

 angles as are the main points themselves. Next, among these irregular figures, 

 though many of them are large and fair ; yet from these taking our first item, 

 many others, alike irregular, but much smaller, may likewise be discovered. 



* Later observations have served to establish the period of revolution of this satellite, which is the 

 5th in order, at 73 days 7h. 48m. 



