April 1, 1904.] 



SCIENCE. 



52i 



gabbro rock 40 feet above the present limits 

 of waves, approximating that done at the 

 sea margin of to-day. Glacial drift has 

 apparently been largely removed through 

 wave action. On the lower Matinicus 

 Group, which lies some twenty miles to the 

 eastward, banks of what seems to be glacial 

 drift are now being rapidly cut away by 

 the sea. Had these two groups of islands 

 taken part in the same movements permit- 

 ting the strong bench cutting in the hard 

 rocks of Monhegan, the preservation of the 

 yielding till has yet to be explained. A 

 suggestion from this evidence is that the 

 recent movements have not been continuous 

 throughout the region. 



The Two Classes of Topographic Belief: 

 George Carroll Curtis. (Read by 

 title.) 



During the last few years there has been 

 both in this country and in Europe discus- 

 sion in regard to the 'proper method' for 

 representing the surface of the earth in 

 relief. Some of this discussion has been, 

 it appears, over two distinct kinds of work 

 Tinder a single classification. These two 

 classes, though not yet generally designated 

 hy separate terms, are labeled here as 

 Classes I. and II. 



CLASS I. 



Requisites of Class I. 



A miniature or repliea of the earth's surface. 



A characteristic reproduction of the topographic 

 form. 



As to scale; true. 



Detail of form; in same proportion as general 

 scale. 



Color; consistent with natural laws. 



Culture; indicated by the forms which char- 

 acterize it. 



CLASS II. 



Attributes of Class II. 

 An expression of a map in relief. 

 An arbitrary representation of the topographic 

 iorm. 



As to scale; optional. 



Detail of form; according to choice. 



Color; any desired scheme or pattern. 



Culture; indicated by any method or arbitrary 

 sign which may seem desirable. 



While these requirements and attributes 

 cover but a portion of the subject, they 

 may serve to illustrate the principles un- 

 derlying it. Should Class I. be designated 

 as topographic models and Class II. as re- 

 lief maps (or by any more appropriate 

 names) Class I. would include poor 'models' 

 and Class II. good 'relief maps.' A poor 

 'model' would be one which, while attempt- 

 ing to follow the principles governing its 

 class, does so in an unskillful and inex- 

 pressive manner. The requirements of a 

 good ' relief map ' are more difficult to state 

 since, being of empirical character, based 

 upon standards of choice, the style of relief 

 maps may be subject to changes of fashion. 

 It seems reasonable, however, to assume 

 that the most satisfactory work in Class II. 

 will eventually be based on a thorough un- 

 derstanding of the principles governing 

 Class I. 



PAPERS READ BEFORE THE GEOLOGICAL 

 SOCIETY OF AMERICA. 



Observations on the Geography and Geol- 

 ogy of Western Mexico: Oliver C. 

 Farrington. (Illustrated by lantern 

 slides. ) 



This paper describes a journey from 

 Dur.ango westward to Ventanas across the 

 plateau of the western Sierra Madre. The 

 plateau exhibits a comparatively unbroken 

 surface rising gradually from a height of 

 6,000 feet at Durango to about 9,000 feet 

 farther west. It then slopes toward the 

 Pacific and is deeply dissected by streams. 

 Evidence is adduced to show a rather rapid 

 eastward movement of the divide. The re- 

 gion is for the most part comparatively arid, 

 although on the western edge of the plateau 

 extensive forests occur. The rocks are 

 largely eruptive. The Carro Mercado or 

 'Iron Mountain' is described in some detail 

 and its origin -discussed, as is, also an area 



