The Central Mass of (he Globe in a state 0/ Igneous Fusion. 209 



answer, which I think may prove both interesting and amusing to your 

 geological readers, and which I therefore enclose. 



I remain, your old correspondent, 



W. D. CONYBEARE. 



" You desiderate information concerning the tides of the nether 



regions. As I cannot get any satisfactory ebb and flow in the Pacific, I 

 am quite disposed to look for any thing of the kind which is to be found 

 lower down. Flectere si neqiieo superos Acheronta movebo. There are 

 no tides at Otaheite, but I do not see why Phlegethon and Cocytus should 

 not alternately boil and simmer, and produce, twice every infernal day, a 

 bore as loud and fierce as the Bristol Channel itself. Nevertheless we 

 must give the devil his due and no more, and not flood his " burning soil" 

 with lava every morning and evening, in a manner contrary to law. Now 

 as to the tides of the central incandescent fluid which the laws of nature will 

 produce, I do not think they can be engineered so as to do the work which, 

 it appears from your letter, Lyell wants to put upon them. You may take 

 two hypotheses ;— first, that the surface, of the infernal ocean is not free, 

 but that the fluid fills its cavities, being open only at certain orifices. lu 

 that case it will be as you say j the effect of the solilunar force will be a 

 pressure equivalent to the weight of the tide which would be produced] that 

 is, to a stratum, say, of six feet high of lava, and the eff'ect of this will be to 

 diminish by so much the downward pressure of the superincumbent rocks; 

 that is, on your supposition, to diminish the effect of more than thirty miles 

 of rock by six feet, in addition to which you have the cohesion of the rock on 

 the conservative side. This could not do any serious mischief. On this sup- 

 position too, I conceive, there would be no jets, but only a rise and fall, very 

 quiet, of the above-mentioned six feet in the open orifices; for the requisite 

 transferor fluid will be made by small and tranquil movements. But if the 

 subterraneous ocean swill about in vaulted caverns, supporting themselves, 

 you may have a tide-wave exaggerated by resistance, contraction, &c. as you 

 denizens of the Severn well know, and thus you may have jets and squirts. 

 This however is a hypothesis which does not appear to be contemplated 

 by those who make a universal fusion of the central part of the globe. 

 You will find that Cordier makes his crust of the earth bend to the oscilla- 

 tions of this central fluid, though I suppose only now and then, in case 

 of volcanic and terraraotive operations. ' Nous sommes arrives a con- 

 naitre,' lie says, ' que cette ecorce jouit vraisemblablcmcnt d'une certaine 

 flexibility.' 



1 conceive too that even allowing the central fluidity, the viscous nature 

 of the substance, at least of the superficial parts of it, will neutralize all 

 tide waves ; this comes to nearly the same thing as thickening the crust, 

 not quite j for, by the viscosity, the force which resists tlie inequality of 



