Dec. 14, 1857.] GALTON ON THE EXPLORATION OF ARID COUNTRIES. 73 
carry a large surplus store of water, as may be understood from the 
following considerations : — 
Farthest point 
Main Camp. Halfway Station. intended to be reached. 
(A) (B) (0) 
^ . — e — 9 
All tlie sections that turn back at B, or short of B, have time to 
return to A, reprovision themselves there, start afresh, and meet 
the exploring party on its return to B : because, from B to A and 
back again to B is exactly equal, in days* journey, to the distance 
from B to 0 and back again to B. If the explorers returned pre- 
maturely, the meeting would take place between A and B. 
When the individuals composing the relief party travelled on 
their first journey, they had not only to feed and to cache for them- 
selves, but they had also to feed and cache for the exploring party, 
and perhaps for other sections also ; but, when they travel as a 
relief party, the equivalent to these latter supplies remains on hand 
as a clear overplus, to be disposed of for purposes of relief. It some- 
what complicates the question to attempt the method of repetition 
with relief parties; however, the first section can always be re- 
dispatched immediately after its return to camp, with a heavy load 
of provisions to cache at the end of the first stage, where it will meet 
the second section, and whence it will return with it to camp, and 
then, having reprovisioned themselves, they may start afresh as a 
relief party. 
Conclusion . — It would take far too much space if I were to attempt 
to enter minutely into many particular cases, and it would be unne- 
cessary if I did so, because no adventurer would ever attempt a 
more complicated experiment than that I am about to describe 
without having repeatedly practised his party at simpler ones, 
neither would he undertake the simplest one without having had 
sufficient rehearsal of it on a small scale to satisfy himself and his 
associates that they understood it perfectly. 
The general rules to be adopted are to keep to steady day’s work, 
neither more nor less ; to mark the roads, and number the camps, so 
that there can be no possibility of mistake about either of them ; and 
to make the cleverest caches they can. Very little delay need be 
apprehended from the straying of cattle, as they would soon learn 
to crowd to the camp, as to a water-tank, when they were thirsty. 
For the purposes of caching and conveying water, and most kinds 
of food also, I know of no plan equal to that of employing one-gallon 
or half-gallon tins painted white, and packed securely with grass in 
strong hampers. 10 lbs. weight of water, or an imperial gallon, con- 
tains 277 cubic inches: and the canisters that appear to me most 
