38 



THE GEOLOGIST. 



numerous ; experienced geologists ever must be few, ~No men possess 

 greater advantages for obtaining and elaborating some at least of the re- 

 quired facing-stones of the huge superstructure of geology than the Di- 

 rectors of National Surveys, no other men have the means at their disposal 

 in time, money, or assistance, still less of obtaining the intercommuni- 

 cation with foreign surveys ; but instead of grand works such as Agassiz' 

 * Fossil Fishes,' Hutton's ' Coal Plants,' Owen's 4 Odontography,' D'Or- 

 bigny's 4 Palaeontology of France,' Mallet's 4 Earthquake Phenomena,' and 

 the publications of the Palgeontographical Society, we must be content to 

 buy for our children the "little books " which those great men we wish to 

 look up to, write for our publishers. Luckily, we have no reason to dread 

 a Murchison penning a geological primer for infant schools. 



But to take the book as it is, and to view it as one for those who have 

 not time for much study, it is better calculated to give the best running 

 notion of geology with the least amount of trouble of any book we know. 

 The popular doctrines of geology are fairly and moderately put, and al- 

 though adhering to many of the views which we ourselves have shown a 

 strong antagonism to in the pages of this journal, Mr. Jukes puts them 

 fairly, and, for a school treatise, properly. Such a work is not an arena for 

 controversy, nor would it be fitting in it to go too strongly against the 

 stream of general belief, and it is therefore better and wiser to teach what 

 is generally accepted, and when to that which is not certain the author 

 adds a statement to that effect, he has done all that is required of him. 

 TJiis Mr. Jukes does most fairly, according to his conscience. Take the 

 account of the igneous rocks as an example, on which, after stating the 

 grounds which geologists urge for a molten state of the interior of the 

 globe, and showing that if the temperature increased regularly with 

 depth, as it is supposed to do, say 1° F. for every 100 feet, or 52° F. for 

 every mile, that at four miles deep water would be at boiling-point, at fifty 

 miles the heat would be sufficient to melt steel, and that at a hundred 

 miles the temperature would be 5000° F., which, Mr. Jukes says, is "greater 

 than any that we know at the surface." 



" It is not by any means necessary, however, to suppose that the temperature does in- 

 crease indefinitely into the interior, or that the rate which regulates its increase near the 

 surface continues to be the same for such depths as those mentioned above. Neither 

 does it follow that the materials, whatever they may be, which exist at great depths, 

 would be melted by the same amount of heat that would fuse them at the surface, since 

 the enormous amount of pressure which they must experience, may keep them solid in 

 spite of the heat." 



After this usual supposititious evasion of the discussion of the great diffi- 

 culties attending the 44 molten interior " doctrine, Mr. Jukes praiseworthily 

 adds a concluding sentence to his chapter : — 



" Little or nothing," he says, " is known about the constitution or condition of the 

 interior, nor have we any grounds even for speculation, further than those which have 

 been previously mentioned." 



The same moderate expression of views of which we have given an ex- 

 ample from the first pages, continues throughout to the end, and from the 

 last page we take another similar extract : — 



te The term 'transition' was at one time used to designate an imaginary period between 

 that of the formation of the so-called crystalline rocks and the others. Part of the same 

 prejudice still lingers amongst geologists, and induces them to regard the present time as 

 distinct from the Tertiary epoch, and to introduce such terms as Fost-Tertiary cr 

 Quaternary." 



