344: GREEK SCIENCE. 



diminishes, as the diameter of this satellite appears to increase or de- 

 crease ; we know, also, that it is greatest and least at the extremities 

 of the line of the apsides of the lunar orbit. Ptolemy observed that 

 from one revolution to another, the absolute quantities of these two 

 extreme velocities varied, and that the more distant the sun was from 

 the line of the apsides of the moon, the more the difference between 

 these two velocities augmented ; whence he concluded that the first 

 inequality of the moon, which depends on the eccentricity of its orbit, 

 is itself subject to an annual inequality, depending on the position of 

 the line of the apsides of the lunar orbit with regard to the sun. 



When we consider Ptolemy's system of astronomy, as founded upon 

 a false hypothesis, the complication of his various epicycles, in order 

 to account for the several phenomena of the heavenly bodies, and the 

 rude state of the ancient astronomy, it is impossible to withhold our 

 admiration of the persevering industry and penetrating genius of this 

 justly-celebrated philosopher; who, with such means, was enabled to 

 discover an irregularity which would seem to require the most delicate 

 and refined aid of modern mechanics to be rendered perceptible. 



The work of this author to which we have hitherto confined our 

 remarks, is the ' Almagest;' 1 but Ptolemy also composed other trea- 

 tises ; which, if not equal to the above in importance, are still such as 

 to be highly honourable to his memory and talents, particularly his 

 geography. 



Ptolemy's This work, although imperfect as to its detail, is notwithstanding 

 geography. f oun( j e( j U p 0n correct principles ; the places being marked by their 

 latitude and longitude agreeably to the method of Hipparchus. As 

 to the inaccuracies of their position, although they cannot be denied, 

 they will readily be pardoned, when we consider that he had for the 

 determination of the situation of cities and places of which he speaks, 

 only a small number of observations, subject to considerable errors ; 

 and the mere report of travellers, whose observations we may readily 

 grant were still more erroneous than those of his own. It requires many 

 years to give great perfection to geography : even in the present time, 

 when observations with accurate instruments have been made in every 

 part of the globe, we are still finding corrections necessary ; a remark- 

 able instance of which seems to have occurred lately (1818) to 

 Captain Ross, in his voyage into Baffin's Bay, where he is said to have 

 found some parts of the land laid down nearly a degree and a half out 



1 The first printed edition of this celebrated performance was a Latin translation 

 from the Arabic version of Cremoneus ; which, however, abounds so much in the 

 idiom of that language, as to render it nearly unintelligible, without a constant 

 reference to the Greek text. This was published at Venice in 1515 ; and in 1538 

 the collection appeared in its original language, under the superintendence of Simon 

 Grynaeus, at Basil, together with the eleven books of the Commentaries of Theon. 

 The Greek text was again republished at the same place, with a Latin version, in 

 1541 ; and again, with all the works of Ptolemy, in 1551 ; and lastly, a splendid 

 French edition, with the Greek text, by M. Halma, in three beautiful volumes, royal 

 quarto, Paris, 1813. 



