February 1, 1907] 



SCIENCE 



175 



tory of the United States, in which, among 

 other less important chapters, the chapters 

 on the Revolution and the Civil War are 

 lost. 



CONCLUSION 



I have not attempted to give a history 

 of geological investigation in this country. 

 Of the great number of earnest and able 

 investigators whose names illustrate the 

 scientific history of this country — of those 

 who have finished their work, but whose 

 memory and influence can never die — of 

 those still living whose achievements in the 

 past are only the promise of greater work 

 in the future— I have named but few, 

 though many others are equally worthy. 

 Of the men whose names I have mentioned, 

 I have doubtless not in all cases mentioned 

 the work which has been most meritorious 

 or important. I have mentioned only those 

 investigations which have a bearing on a 

 few special subjects. Nor have I referred, 

 except occasionally and incidentally, to the 

 work of European students which has gone 

 on parallel with that of students in our 

 own country. American geologists have 

 had no patent rights giving them a mon- 

 opoly of any particular department of in- 

 vestigation. The limited time of such an 

 address as the present renders impossible a 

 critical discussion of the precise share in 

 the study of the various subjects which 

 belongs to American geologists. But I be- 

 lieve it may be fairly claimed that on the 

 five subjects which I have discussed — the 

 permanence of continents, the theory of 

 mountain-making, the history of the Gla- 

 cial period, the laws of subaerial denuda- 

 tion, the evolution of mammalian life— the 

 work of American geologists has been rela- 

 tively so important that the results deserve 

 recognition as, par excellence, The con- 

 tributions OF America to geology. 



William North Rice 

 Wesletan University 



SCIENTIFIC BOOKS 

 The Development of Symbolic Logic: A Crit- 

 ical-Historical Study of the Logical Cal- 

 culus. By A. T. Shearman, II.A. London, 

 Williams and ISTorgate. 1906. 

 As the subtitle indicates, the author has 

 attempted a history of symbolic logic accom- 

 panied by a critical examination and estimate 

 of the various systems as they may have con- 

 tributed severally to the discipline from its 

 earliest stages to the present time. He claims 

 that in spite of the great variety of systems 

 and methods there is clearly to be recognized 

 but one logical calculus, and that the unity 

 among the various symbolists abundantly com- 

 pensates for the obvious differences. While 

 this is true it should not be overlooked, how- 

 ever, that the progress of symbolic method has 

 been retarded owing to the lack of a common 

 symbolism such as we find in mathematics. 

 The variety and the multiplicity of symbolical 

 representation is, in my opinion, a serious 

 defect. It is not merely that different writers 

 are using different methods of symbolism — 

 that in itself is sufficiently confusing — but 

 also that any new operation is apt to give rise 

 to some entirely new form of symbolism which 

 might be represented equally as well by some 

 new combination or new manipulation of the 

 existing syinbols already at hand. Within the 

 scope of a few elementary symbols an indefi- 

 nite range of differing processes and devices 

 is possible, just as in mathematics the symbols 

 used are exceedingly few — but they lend them- 

 selves easily and adequately to the exact ex- 

 pression of an innumerable array of opera- 

 tions and processes. The desideratum in a 

 symbolic logic is, therefore, twofold: a com- 

 mon and a simplified symbolism. The sim- 

 plicity of the symbolism of Leibniz, the found- 

 er of symbolic logic, is most striking; but the 

 drift has been from this characteristic sim- 

 plicity towards increasing difference and com- 

 plexity. The author, by the way, does not 

 give Leibniz his full due as the founder of the 

 symbolic logic. Mr. Shearman insists that 

 Boole is to have the complete credit of this on 

 the ground that Boole worked independently 

 and without any knowledge of the early work 

 of Leibniz. The latter assumption seems 



