572 



SCIENCE. 



[N. S. Vol. VII. No. 173. 



something else must be devised than the exist- 

 ing cumbersome and unsatisfactory scheme of 

 vaguely defined geological formations, having 

 no comparable limits in the different geological 

 provinces and even diverse values in the same 

 province, some plan that must be natural and 

 at the same time elastic. Practical experience 

 in the field and the demands of the times soon 

 pointed out a feasible scheme. So well has it 

 served the purpose, and so readily adaptable is 

 it to the changing conditions met with on all 

 sides and to all the unforeseen exigencies con- 

 tinually arising, that it has brought under its 

 standard nearly every practical field geologist. 



The present method of designating geological 

 formations by geographical names certainly 

 does greatly expand the nomenclature at times 

 seemingly to a burdensome extent. This ap- 

 pears to be the only objection that has been 

 urged against the plan that might call for no- 

 tice. Yet, to all except those who do not wish 

 to go beyond the ordinary text-book in geo- 

 logical work, even this seems hardly worthy of 

 special argument, since it is offset by so many 

 manifest advantages. 



It may be truly said that no greater boon to the 

 working, as well as to the theoretical, geologist 

 has been devised. Incorporated in the new plan 

 are practically all of the salient good features of 

 the old method, while none of the many objec- 

 tionable ones are retained. Since its adoption a 

 vast mass of exact information has been ob- 

 tained that was previously unthought of — in- 

 formation that is in shape to be always used, 

 without the necessity of going all over the 

 ground again; the other departments of geology 

 have been greatly aided, and stratigraphical 

 geology itself has been capable of making greater 

 real progress in the one short decade that has 

 elapsed since the method came into use than 

 in all time previous. In the same short period 

 more has been learned about the real nature of 

 sedimentation, the actual relations existing be- 

 tween different rock formations and the struc- 

 ture of the layered cuticle of the globe, than 

 was possible before. In fact, a rational basis 

 for geological correlation and a genetic classifi- 

 cation of formations has been found. 



The real meaning, then, of the multitude of 

 new titles that has recently made its appear- 



ance in the literature of stratigraphy is the 

 practical adoption of more refined methods of 

 geological work, the provision of means for the 

 collection of more exact geological data and the 

 grasping of more rational conceptions regarding 

 geological correlation and classification. 



Charles R. Keyes. 



SCIENTIFIC LITERATURE. 

 Die Farnhrauter der Erde. By H. Christ. Jena, 



Gustav Fischer. 1897. Mit 291 Abbil- 



dungen. 8vo. Pp. 388. 12 M. 



In the preparation of such a work as the 

 above one is expected either to have in mind 

 the filling of a felt want, or at least to furnish a 

 sufiicient reason for the expenditure of so much 

 energy. Neither of these seems to have been 

 considered in the present case, if we judge of 

 the work by the test of completeness which the 

 title would lead us to expect. The purpose of 

 the work seems to be the presentation of the 

 general systematic relations of the genera and 

 characteristic species of ferns, without attempt- 

 ing completeness either in the flora of a given 

 region or the full quota of species of any par- 

 ticular group. As a manual for the identifica- 

 tion of species its value can only be slight, as it 

 is most likely to be deficient at the point where 

 it is most needed, for usually there is no sugges- 

 tion whatever of the nature, distribution or 

 number of the allied species, and the specific 

 descriptions that are given are not uniformly 

 full, many of them being very incomplete. 

 The work will be useful within narrow limits, 

 however, particularly among florists and those 

 to whom scientific accuracy is not so uni- 

 formly important. It describes more or less 

 completely 1154 species of ferns, which, at a 

 moderate estimate, cannot much exceed one- 

 third of the known species of the world. 



The system of classification is not strikingly 

 novel, following in the main that of Mettenius 

 and Prantl. While the number of recognized 

 genera (99) is considerably larger than that rec- 

 ognized at Kew, which has been followed in 

 this country, it will by no means satisfy those 

 who regard genera, among ferns as elsewhere, as 

 natural groups of organisms closely connected 

 in habit and other biological characters, instead 

 of artificial groups thrown together for conven- 



