568 Notices of Memoirs—Edward A. Reeves-— 
I have attempted to form an estimate of the condition of the 
world’s surveys as represented by the differently tinted areas on the 
maps for 1860 and 1916;' and, taking the total area of the land- 
surface of the earth, together with the unknown parts of the Arctic 
and Antarctic regions which may be either land or water, to be 
60,000,000 square miles, I have obtained the following results :— 
1860 1916 
Sq. Stat. Proportion Sq. Stat. Proportion 
Miles. to Whole. Miles. to Whole. 
1. Mapped from accurate ed 
graphical surveys based on| 1,957,755=0°0326  8,897,238=0°1482 
triangulation or rigorous | or roughly #5 or roughly + 
traverses 
2. Mapped from less reliable lees bay 
surveys, chiefly non-topo- Ge ck on ait a as, ee. 
graphical rion: hae 
3. Mapped from route traverses\ 25,024,360=0°4170 37,550,552—0°6258 
and sketches ah or roughly 2 or little less than 2 
4. Entirely unsurveyed and) 30,997,054=0-5166 8,350,794=0°1391 
unmapped { J or just over 4 or little less than + 
These proportions can perhaps be more clearly seen from the 
following small diagram. 
1860 19 16 
Diagram showing the relative proportions of the earth’s surface in 
1860 and 1916, which are—1, fully mapped; 2, partially mapped ; 
3, slightly mapped; and 4, not mapped in the two periods 
referred to. 
It is plain that with the same rate of progress as that of the past 
sixty years or so it would take just over four hundred years more ~ 
1 The two maps have not been reproduced from Mr. Reeves’ Address, but 
the small diagram is given and shows the areas mapped and unmapped and 
their relative proportions. 
