The first cardinal particular we meet with in the above statement concerning the sun, is the term, distance. Now, all that, strictly speaking, we can affirm respecting the sun and other heavenly bodies, is that we have the same series of impressions respecting them, that we have respecting terrestrial objects near or remote, and that there is an imperfect analogy between the one case and the other. Before we affirm any thing, as of our own knowledge and competence, respecting heavenly bodies which are said to be millions of millions of miles removed from us, it would not perhaps be amiss that we should possess ourselves of a certain degree of incontestible information, as to the things which exist on the earth we inhabit. Among these, one of the subjects attended with a great degree of doubt and obscurity, is the height of the mountains with which the surface of the globe we inhabit is diversified. It is affirmed in the received books of elementary geography, that the Andes are the highest mountains in the world. Morse, in his American Gazetteer, third edition, printed at Boston in 1810(46), says, "The height of Chimborazzo, the most elevated point of the vast chain of the Andes, is 20,280 feet above the level of the sea, which is 7102 feet higher than any other mountain in the known world:" thus making the elevation of the mountains of Thibet, or whatever other rising ground the compiler had in his thought, precisely 13,178 feet above the level of the sea, and no more. This decision however has lately been contradicted. Mr. Hugh Murray, in an Account of Discoveries and Travels in Asia, published in 1820, has collated the reports of various recent travellers in central Asia; and he states the height of Chumularee, which he speaks of as the most elevated point of the mountains of Thibet, as nearly 30,000 feet above the level of the sea. (46) Article, Andes. The elevation of mountains, till lately, was in no way attempted to be ascertained but by the use of the quadrant, and their height was so generally exaggerated, that Riccioli, one of the most eminent astronomers of the seventeenth century, gives it as his opinion that mountains, like the Caucasus, may have a perpendicular elevation of fifty Italian miles(47). Later observers have undertaken to correct the inaccuracy of these results through the application of the barometer, and thus, by informing themselves of the weight of the air at a certain elevation, proceeding to infer the height of the situation. (47) Rees, Encyclopedia; article, Mountains. There are many circumstances, which are calculated to induce a circumspect enquirer to regard the affirmative positions of astronomy, as they are delivered by the most approved modern writers, with considerable diffidence. They are founded, as has already been said, next to the evidence of our senses, upon the deductions of mathematical knowledge. Mathematics are either pure or mixed.