Theory of the Earth, ^c. 85 



commotion would be produced in the atmofphere, which would conliriuc for years, until 

 all the parts were united about the common centre*. 



III. Concerning the earth and the moon. — That the earth is a ftar ; that the fcintillation 

 of the flars is an aiFedlion of the eye +; that the earth performs the fame office of illumi- 

 nation to the moon, as the moon to the earth, but with contrary phafea ; that the earth in 

 lunar eclipfes does not receive light by reflection from the moon, mr the moon from the 

 earth in folar eclipfes ; that the obfcure illumination of the dark part of the moon at the 

 beginning of the firft and end of tlie lafl quarters is produced by rcfle£lion of folar light 

 from the earth. 



IV. On the adlion of the fun upon the ocean. — Our author affirms that the heat of the 

 fun caufes the waters of the fea to rife in an eminence beneath the equator, from which 

 tliey flow on all fides, as may be obferved in water heated over a fire ; and that the aqueous 

 eminence following the fun in the diurnal motion is carried through about a thoufand 

 miles per hour. 



De Vinci has here applied the fame principle to the waters of the ocean, as Halley has 

 fince ufed to explain the trade winds in the atmofphere J. 



V. The ancient Hate of the earth. — When the water of rivers depofited its mud upon the 

 marine animals living near the fliore, this mud imprefled itfelf upon the animals thera- 

 felves. When the fea afterwards retired, this mud became petrified all round, and within 

 the fliells of teftacea which it had penetrated. Thefe are found in various places ; and 

 moft of the fliell-filh petrified in the mountains have their fliells entire, particularly thofe 

 of the greatell age and hardnefs. In anfwer to a fuppofed objedion, that the influence of 

 the liars may have formed thefe fliells in the mountains, the author requires to be Ihewn 

 any place where this operation of the flars is in aftual progrefs to form fhells of difl^erent 

 ages and fpecies in the fame place. And how upon that fyftem it can be explained why 

 the gravel has become indurated in ftrata at different heights in the mountains. This 

 gravel, continues he, has been tranfported thither from various places by the currents of 

 rivers. It was formed of fragments of ftone, of which the corners have been worn down 

 by the frictions, blows, and falls they have undergone in the water which rolled them to 

 their prefent fituation. And how can this fyftem explain the great number of different 

 kinds of leaves bedded in ftone near the tops of mountains ? and the Alga, a marine 

 plant, intermixed with fliells and fand, and petrified in a mafs with fea crabs broken and 

 confounded with the fame fliells. 



* In thisfeftion it is evident, as ProfelTor Venturi remarks, that our author has a clear comprehenfion of the 

 inertia of matter. Another ftep in the procefs of rcafoning would have given a revolution, to his falling frag» 

 ment, in an apprq>riate orbit. The vibration of a body in a cavity through the centre of the earth to the anti, 

 podes, and the retention of the moon in its orbit by the combination of the projeft'.le and gravitating forces 

 are ftated in a palTage of fome length by Plutarch, in his crem(e De flat t'tis fhilofopherum, as I well remsmbtr, 

 but have not the work at hand to quote. N. 



f On this fubjeft it may be remarked in favour of fcintillation being a confequcnce of the irregular denfity 

 of the air, and not an affeftion of the eye, i. That itii lefs on lofty mountains, and countries where the air is al- 

 moft conftamly ferenc. a. That in the fame ftar it is lefs, the greater the altitude. Andj. That, contrary to^ gcf. 

 iieral obfcrvation, it may be obferved through a tclefcope, provided the difc of the ftar be eniar^^ed hj deran- 

 ging the focal adjuftmcnt. N. 



+ And very lately again applied to the fe» by Count Rumford. Phibf. Jourual, I. 573. N. 



Thc^ 



