September 11, 1885.] 



SCIENCE. 



217 



PROBLEMS IN THE STUDY OF COAL, 

 WITH A SKETCH OF RECENT PROG- 

 RESS IN GEOLOGY.^ 



We have again assembled in our annual council, 

 to renew and extend our acquaintance with each 

 other, to maintain and strengthen the esprit de corps 

 which ought to characterize the workers in a common 

 field, to share with each other the new facts and new 

 conclusions that we have reached by the labors of 

 the last year, mente et malleo, and especially to aid 

 each other in securing larger and more symmetrical 

 views of the truths we hold, by fraternal discussion, 

 criticism, and correction. 



To review the record of the last year, and gather up 

 its most significant advances, would be appropriate 

 to the occasion; but various limitations forbid me to 

 undertake such a task in any formal way. Before 

 entering, however, upon the discussion of the subject 

 which I wish to present to you, I beg leave to call 

 your attention to a few facts that seem to me of spe- 

 cial interest ; and also to point out, in like cursory 

 manner, some of the special directions and subjects 

 in which American geology seems to me to be show- 

 ing the most activity and progress at the present 

 time. 



The history of the vertebrate life of the globe, as 

 far as it is now written, indisputably owes some of its 

 most interesting and important chapters to American 

 geology; but up to the last year we were still obliged 

 to recognize the Ludlow rocks of Great Britain as the 

 depositories of its earliest known forms. The recent 

 fortunate discovery of the pteraspidian type of fishes 

 in the Onondaga group of central Pennsylvania, by 

 our associate. Prof. E. W. Claypole, has, however, 

 granted us an equal date, at least, with the Scaphaspis 

 of the lower Ludlow; and a fair argument can be 

 made as to the somewhat greater antiquity of the 

 Pennsylvania forms. This argument it is not neces- 

 sary to press; for it loses its point and interest in the 

 light of Professor Claypole's subsequent discovery of 

 well-marked scales and spines of fishes in the iron 

 sandstone of the middle Clinton group of central 

 Pennsylvania. Onchus Clintoni of Claypole must 

 enjoy the distinction, at least for a little time, of 

 being recorded as the earliest representative of the 

 vertebrate life of the globe. 



But the ' earliest vertebrate ' always sits on a preca- 

 rious throne. At any moment the title is liable to 

 lapse. To see its horizon suddenly descend several 

 thousand feet in the scale, scarcely awakens our sur- 

 prise. The abrupt appearance, the great numbers 

 and the comparatively high organization of the earli- 

 est American fishes heretofore known, all demand a 

 long antecedent history; and it is therefore no unwel- 

 come labor to erase the old boundaries, and to draw 

 the new ones, in such a way as to gain protracted 

 ages for the unfolding and development of the type. 



Another fact in the history of vertebrate life, ac- 



1 Abstract of an address delivered before the section of geology 

 and geography of the American association for the advancement 

 of science, at Ann Arbor, Aug. 26, by Professor Edward Orton, 

 State geologist of Ohio, vice-president of the section. 



quired during the past year, deserves special mention 

 here. Mr. Samuel Garman has recently published a 

 description of a living shark that proves to be a 

 cladodont, and so nearly allied to the genus Cladodus 

 of carboniferous time, that it might with little vio- 

 lence be referred thereto. According to present 

 knowledge, the family of cladodonts originated in 

 the middle Devonian; and the genus Cladodus, as we 

 have hitherto been obliged to hold, became extinct 

 in the same age that gave it birth: but the chance- 

 catch of a Japanese fisherman gives us an unmistak- 

 able cladodont, if not a true Cladodus, to-day; and in 

 it we find ' the oldest living type of vertebrates.' The 

 gap is far wider than any that has been heretofore 

 bridged. 



The discovery during the last year of fossil scor- 

 pions in three quite widely separated portions of the 

 world at horizons approximately identical, and at 

 the same time vastly lower than any in which they had 

 been found hitherto, is a fact of much geological in- 

 terest and significance. These three specimens from 

 the upper Silurian effect an immense extension of 

 the history of the tribe to which they belong, but 

 each of them still falls short of the title of the ' ear- 

 liest known land-animal.' That distinction is, for 

 the present, held by the representative of an allied 

 division. From well-characterized strata of middle 

 Silurian age in central France, there was obtained 

 during the past year tlie fragment of a cockroach's 

 wing. It is a surprise to find Blatta, for the time 

 being, at the head of the line of the inhabitants of 

 the dry land. 



Within the last year our associate, Mr. C. D. Wal- 

 cott, has published a description of two species of pul- 

 moniferous moUusks from the lower portion of the 

 carboniferous rocks of Nevada. Both belong to the 

 aquatic section of the Pulmonifera, and constitute 

 the sole known representatives of that group in pale- 

 ozoic time. One of them is a true Physa, and thus 

 gives to this humble form a vast antiquity. 



But leaving, witliout further notice, these very sug- 

 gestive facts, let us barely glance, in passing, at some 

 of the chief features in the advance of geological 

 knowledge among us at the present time. 



In the first place, stratigraphical geology appears 

 to me to be attaining a somewhat juster recognition 

 than has hitherto prevailed. It has been made very 

 clear, that the work of the paleontologist is still too 

 incomplete to allow any off-hand settlement of many 

 of the questions that arise, by his determinations. 

 There has been, in my judgment, an undue tendency 

 to settle all questions as to the age and order of the 

 several strata of any considerable series by the tes- 

 timony of a few fossils. In the second place, the 

 growing use of the microscope in geology is to be 

 noted as one of the directions in which progress is 

 apparent and marked. Tliere is scarcely a field of 

 research in which the service of the thin section is 

 not now acknowledged and invoked. By it most of 

 the varied claimants to the early life of the globe 

 must be tried; and by it, as well, the minerals of the 

 igneous and metamorphic rocks must be finally deter- 

 mined. Let us glance next with equal brevity at two 



