570 Notvces of Memoirs—The Mapping of the Earth. 
of the Pamirs. The many boundary surveys that have been carried 
out in Africa, the triangulations of Egypt, the Soudan, Kast and 
South Africa, and other parts of the continent are well advanced, 
and will be of the utmost value to the future surveyor. One of the 
most important lines is the great triangulation which, it is hoped, 
will some day run across the continent from south to north, from the 
Cape to Egypt. Owing to the energies of the late Sir David Gill, 
this important chain of triangles has already got as far as the southern 
end of Lake Tanganyika; the part to the west of Uganda near 
Ruwenzori has also been finished, and it now remains to carry the 
chain through German East Africa and down the Nile Valley. The 
latter, it is hoped, will by degrees be accomplished by the Soudan 
and Egyptian Survey Departments, although it may be delayed for 
some years yet; and the former, which was to have been undertaken 
by the Germans, it is hoped will after the War be accomplished by 
British surveyors, through—not German East Africa—but newly 
acquired British territory. Running right through parts of Africa 
that are but imperfectly mapped in many districts, the stations of 
this triangulation will be invaluable for the adjustment of any network 
of triangulation for future surveys in the interior, and, indeed, has 
already been utilized for the purpose. 
The carefully carried out boundary surveys between various countries 
of South America will be of the greatest assistance in future explora- 
tion and survey in the interior of that continent, wherever they are 
available, while the Survey Departments of Canada and the United 
States are doing excellent work and extending their surveys far into 
the imperfectly mapped regions of North America. So, altogether, 
the surveyor of the future will soon have a good foundation of 
reliable points to work from. It is important to remember that 
running a chain of triangles across a country, though important as 
a framework, does not constitute a map of the country; and what is 
wanted, at any rate in the first place, is a series of good topographical 
maps, based upon triangulation, showing the leading features with 
sufficient accuracy for the purposes of ordinary mapping, so that on 
scales of 1 : 250,000 or even 1: 125,000 there is no appreciable error. 
As regards instruments, the Astrolabe 4 Prisme is being increas- 
ingly used for taking equal altitude observations with most excellent 
results, but at the present time the 5 in. transit micrometer theodolite, 
already referred to, is perhaps all that is required for general work. 
It has now been thoroughly tested and found most satisfactory. As 
regards smaller instruments, there is the 4 in. tangent-micrometer 
theodolite, and for rapid exploratory survey, where weight is a great 
consideration, a little 3 in. theodolite has been found useful. 
For baseline measurement the Invar tape should be taken on all 
serious work, and for filling in the topographical features a good 
plane-table is doubtless the instrument to use. In mountainous 
regions and in some other special conditions photographie surveying 
doubtless has a future before it, and in military operations when the 
photographs are taken from aircraft it has proved itself invaluable; 
but in ordinary surveying it is, I think, not likely to take the place 
of well-established methods. The introduction of wireless telegraphy 
