210 Reply to Captain Fornian^ s TJieory of the Tides. 



perfectly opaque. The compact felspar has a splintery con- 

 choidal fracture ; the fracture of the claystone, on the other 

 hand, is even, and always smooth. The compact felspar is 

 more or less line in the grain, and the splinters more or less 

 large. The strata of the compact felspar, like those of the 

 greenstone and claystone, are also at times columnar, the co- 

 lumns being composed of small round concentric balls, and 

 very brittle. These balls are at times partially composed of 

 hornstone. This mineral occurs also in the compact felspar, 

 in thin beds, in veins, and in masses ; it;s colour is green, its 

 fi-acturc smooth, conchoidal, it is slighdy translucent on the 

 edges, and is as hard as quartz. 



Claystone again succeeds the compact felspar, and the latter 

 . is again succeeded by the former, thus alternating for about 

 eight or ten miles across the peninsula. The claystone always 

 possesses a slaty structure, and soon decays. The soil over 

 the greenstone and amygdaloid is rich and good, while over 

 the claj'stone and compact felspar it is light and poor. 



XL. Rejdy to Captaifi Forman's Theory of the Tides. By 

 Mr. Henry Russell. 



^ the Editors of the Philosophical Magazine and Journal. 



Gentlemen, — 1 he expansibility of water being a well at- 

 tested fact. Captain Forman's theory will no doubt meet with 

 due attention ; but I am persuaded that very few will be de- 

 lighted with his method of reasoning. 



With regard to his question, " Do the water'; at the time of 

 their rising press downwards, or do they not?" I answer. 

 They press downwards ; but with as much less power as is 

 equal to the attractive power of the moon. 



To the next question, " How are we to account for dieir 

 rising, except by supposing that they are pressed upwards by 

 the expansion of die pardcles below?" I answer. By the su- 

 perior gravity ol those waters which constitute die ebb. 



I do not deny an expansion and contraction of the waters 

 occasioned by die arrival and departure of the moon ; but die 

 circumstance of the highest tides being invariably accom- 

 panied by the lowest ebbs, is alone sufficient to convince any 

 impartial inquirer, that die ebb and flow of die waters are 

 produced by changes of place, and not by rarefaction and con- 

 densation alone. 



The satisfiiction which Mi". Forman seems to derive from a 

 ■ handful of water is by no means enviable. He speaks of 



the 



