Geology by Submarine Researches. 323 



depth are equivalent to parallels in latitude, corresponding to 

 a well-known law in the distribution of terrestrial organic 

 beings, viz. that parallels in elevation are equivalent to paral- 

 lels in latitude : for example, as we ascend mountains in tro- 

 pical countries, we find the successive belts of vegetation 

 more and more northern or southern (according to the hemi- 

 sphere) in character, either by identity of species, or by re- 

 presentation of forms by similar forms ; so in the sea, as we 

 descend, we find a similar representation of climates in pa- 

 rallels of latitude in depth. The possibility of such a repre- 

 sentation has been hypothetically anticipated in regard to 

 marine animals by Sir Henry DeLaBeche,* and to marine plants 

 by Lamouroux. To me it has been a great pleasure to con- 

 firm the felicitous speculations of those distinguished observers. 

 The fact of such a representation has an important geological 

 application. It warns us that all climatal inferences drawn 

 from the number of northern forms in strata containing 

 assemblages of organic remains, are fallacious, unless the ele- 

 ment of depth be taken into consideration. But the influence 

 of that element once ascertained (and I have already shewn 

 the possibility of doing so), our inferences assume a value to 

 which they could not otherwise pretend. In this way, I have 

 no doubt, the per-centage test of Mr Lyell will become one 

 of the most important aids in geology and natural history ge- 

 nerally ; and, in fact, the most valuable conclusions to which 

 I arrived by the reduction of my observations in the -^gean, 

 were attained through the employment of Mr Lyell's method. 



IV. All varieties of sea-bottom are not equally capable of 

 sustaining animal and vegetable life. — In all the zones of 

 depth there are occasionally more or less desert tracts, usually 

 of sand or mud. The few animals which frequent such tracts 

 are mostly soft and unpreservable. In some muddy and 

 sandy districts, however, worms are very numerous, and to 

 such places many fishes resort for food. The scarcity of re- 

 mains of testacea in sandstones, the tracks of worms on ripple- 

 xnarked sandstones, which had evidently been deposited in a 



* Ten years ago, in his *' Researches in Theoretical Geology.' 



