VOL. LI.] PHILOSOPHICAL TRANSACTIONS. 433 



takes notice, that the colours of the stars and planets are the same now as the 

 ancients observed, which is very true in general ; for Ptolemy, in his catalogue of 

 stars, says, Arcturus, Aldebaran, Pollux, Cor Scorpii, and Orion's Shoulder, 

 with another to be mentioned presently, are vTroxippog, reddish : and the 5 here 

 mentioned are still of that colour, and probably the only considerable stars which 

 are so. 



But to this rule there seems to be one exception, and that in a remarkable 

 star: for old authors mention the Dog star, which is now white, and not at all 

 inclined to redness, as being then very much so, as in many passages of their 

 works. 



Hyginus, in distinguishing Cauis from Sirius as two different stars, seems to 

 contradict all other writers, who speak of them as one, except perhaps two or 

 three latter ones, who directly quote Hyginus's words. Sirius, or Canis, the 

 brightest star in the heavens, is that which Ptolemy calls in the mouth ; Era- 

 tosthenes and Hyginus, in the tongue; but whether Bayer y, which Flamsteed 

 calls a 3d magnitude star, Ptolemy only a 4th, was in more ancient times larger, 

 Mr. B. will not pretend to say; since Eratosthenes and Hyginus both speak of 

 two stars in the Dog's head, as thought worthy of particular names. If in Hy- 

 ginus, flammae candorem means the whiteness of its light, as candor often does, 

 he expressly contradicts what is mentioned by others; yet still thinks Ptolemy's 

 authority seems greater than that of Hyginus. But candor is also used for inno- 

 cence, beauty, brightness, &c. 



However in most places candor is used in the same sense as in Hyginus, for 

 brightness, without regard to colour; for so he must be understood, not only to 

 avoid contradiction between him and Ptolemy, but from the name Sirius, which 

 it could not be called from its whiteness, lapjo? bearing no relation to that, but 

 to brightness, heat, or dryness ; all which the ancients speak of as properties of 

 the Dog star. Again, it is brightness wherein it excels all other stars, and not 

 in whiteness; for Orion's foot and others are as white, but there is none so 

 bright as the Dog star. All this is said on supposition there was but one remark- 

 able star in the Dog's head, that in the mouth; for if there were two, as Hyginus 

 says, we are not here concerned with either the brightness or colour of his Sirion, 

 which was in the head, as it certainly faded before Ptolemy's time, who men- 

 tions only one, that in the mouth, and which, he says, was then red, but is 

 now white. 



^LFIII. The Method of making Sal Ammoniac in Egypt; as communicated by 

 Dr. Linneus, from his Pupil Dr. Hasselquist, who had been lately in those 

 Parts. By John Ellis, Esq., F. R. S. p. 504. 

 Sal ammoniac is made from the soot arising from the burnt dung of four- 



VOL. XI. 3 K 



