64 STUDIES, SCIENTIFIC AND SOCIAL CHAP. 



the globe's surface. But even this will not suffice to get 

 an adequate view of the globe in all its parts, and this 

 enormous mass is to be rendered capable of rotating on a 

 vertical axis. It is suggested that this rotation shall be 

 continuous in the space of a sidereal day, and it is thought 

 that it will be so slow as not to interfere with any photo- 

 graphic operations that may be desired. 



But a little consideration will show us that, even with 

 all these complex constructions and movements, and sup- 

 posing that they all work with complete success, the main 

 purposes and uses of the globe, as laid down by M. 

 Reclus himself, would be very imperfectly attained. His 

 first point is that such a globe would correct erroneous 

 ideas as to the comparative size and shape of different 

 regions due to the use of Mercator's or other forms of pro- 

 jection. But in the globe as proposed no comparison of 

 different countries, unless very near together, would be 

 possible ; and even if considerable portions of the plat- 

 form could be removed, and the observer could be placed 

 near the outer covering, at a distance of, say, forty feet from 

 the globe, only a comparatively small area could be seen 

 or photographed in its accurate proportions. If we take a 

 circle of forty feet diameter as our field of view it is evident 

 that all the marginal portion would be seen very obliquely 

 (at an angle of 30 from the perpendicular if the surface 

 were flat, but at a somewhat greater angle owing to the 

 curvature of the surface), and would also be on a smaller 

 scale owing to their greater distance from the instrument, 

 so that the central portions only would be seen in their 

 true proportionate size and shape. For ordinary views 

 this would not much matter, but when we have to produce 

 maps from a globe which is estimated to cost somewhere 

 about a million sterling, and one of whose chief uses is to 

 facilitate the production of such maps, a high degree of 

 accuracy is of the first importance. In order to attain even 

 a fair amount of accuracy comparable with that of a map 

 on any good projection, we should probably have to limit 

 the portion photographed to about ten feet square, equal to 

 190 or 200 miles, so that even such very restricted areas 

 as Scotland or Ireland would be beyond the limits of 



