110 



THE GEOLOGIST. 











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B 



D 



Note on a Pbogbessive Change in the Foem of the Eaeth. — 

 If it be assumed that the earth has cooled to its present temperature from 

 a state of incandescence, it will follow that its form is subject to a slow 

 progressive change. Let A C B D be the spheroid of equilibrium at any 

 epoch, the form of this spheroid depends on its magnitude and the velocity 

 of rotation. If either of these changes, the form will change. Sow let 



the spheroid ACBD contract, by cooling, 

 to the spheroid a c b d, whose surface may 

 be considered as parallel to A C B D ; when 

 the amount of contraction is small, therefore 

 B b is equal to C c. If these equals be taken 

 from both terms of the ratio O B : O C that 

 ratio will be increased ; therefore 0 6:0c 

 is greater than O B : O C ; that is, the equa- 

 torial diameter has a greater ratio to the 

 polar diameter than it had before the con- 

 traction took place. The effect of this is equivalent to a constant accu- 

 mulation of matter at the equator in excess of what is due to the velocity 

 of rotation. This excess could never attain to any considerable magnitude 

 so long as the earth was in a fluid state, as the change would take place 

 per gradum from the old to the new spheroidal form of equilibrium ; but 

 when the external crust became sufficiently rigid to oppose resistance to 

 the change of form, the alteration would take place per saltum at the 

 weakest points. This is probably worthy of the attention of those who have 

 the necessary qualifications for discussing mathematically the difficult but 

 intensely interesting subject — the physical causes of geological phenomena. 

 To those who feel a difficulty in understanding how contraction towards 

 the centre can produce upheavals from the centre, I recommend the fol- 

 lowing experiment. Fuse a bead of carbonate of soda in the blowpipe 

 flame. Dip the bead into a little powder of silex and fuse again. Watch 

 the cooling through a magnifier. Conical hills start up and mountain- 

 chains are formed as if by magic. The experiment may be repeated any 

 number of times with the same bead, which proves that the elevations are 

 not caused by escaping carbonic acid gas, but by the contraction of the ex- 

 ternal cooling surface on the internal fluid mass. — Gr. H. 



Mammalian Remains in the Hampshiee G-eavel. — Sir, — In the num- 

 ber of your periodical for November last. p. 427, you were good enough to 

 publish a communication from me, from which it might be inferred that 

 my inquiries for animal remains, in the gravel deposits of this neighbour- 

 hood, had been fruitless. 



I have since, however, by inquiring of gravel-diggers, been made ac- 

 quainted with, and have to-day seen, a molar tooth of an elephant from the 

 gravel at Swathling, which is a village about three miles east of this town. 

 This is the only instance of the kind in this neighbourhood with which I 

 am acquainted ; but I remember meeting somewhere with the mention of 

 the existence of mammalian remains in the gravel at a locality at the back 

 of the Isle of Wight: perhaps you might be able to tell me if there are 

 any other such fossil-bearing spots, in the gravel, recorded as existing in 

 the county of Hampshire ? 



I was likewise shown to-day a bunch of sea (?) shells from the gravel, 

 also from the neighbourhood of Swathling, but from a different locality to 

 where the first-mentioned fossil was found. W. T. Xicolls. 



Southampton! February 9, 1S63. 



New Species of Fish feom the Ceag. — Dear Sir. — I believe that 

 up to the present time the remains of Placoid fish only have been found in 



