182 THE ANTARCTIC MANUAL. 
in mountainous countries, and also to measure the thickness of 
horizontal beds. A good aneroid gives sufficiently accurate deter- 
minations of height for a rough but adequate geological section across 
any country if the distances are known. 
Abney’s pocket level is a portable and useful instrument. An 
observer, having previously ascertained the exact height of his eye 
when standing upright, can measure the altitude of any point with 
some degree of accuracy; he has only to mark by the level a recog- 
nisable stone or plant, and then to walk to it, repeat the process, and 
keep an account how many times the levelling has been repeated in 
ascending to the point the height of which he wishes to ascertain. 
Rules for Collecting —A few cautions may be here inserted on the 
method of collecting. Every single specimen ought to be numbered 
with a printed number (those which can be read upside down having a 
stop after them), and a book kept exclusively for their entry. As the 
value of many specimens entirely depends on the stratum or locality 
whence they were procured being known, it is highly necessary that 
every specimen collected should be ticketed on the same day. If 
this be not done, the collector will never in after years feel sure 
that his tickets and references are correct. 
Labels should not be put up in contact with the rock-fragments 
themselves, or they will be worn by sharp edges and become illegible, 
if not rubbed to fragments. Always wrap each specimen in paper, 
or some substitute, then add the ticket or label, and then an outer 
covering. The label, if nothing else be written, should always 
record the locality distinctly written, either in ink or by a hard 
black pencil, or better still, a blue indelible pencil. 
Pill boxes are useful for packing fossils. Masses of clay or 
any soft rock may be brought home if small fossil shells are 
abundant in them. A convenient size for rock specimens is 4 inches 
to 44 inches long by 3 inches broad, and one inch to half an inch 
thick. To save subsequent trouble it will be found convenient to 
pack separately, and mark sets of specimens which come from dif- 
ferent localities. These details may appear trifling; but few are aware 
of the labour of opening and arranging a large collection, and such 
have seldom been brought home without some error and confusion 
having crept in; whenever it is practicable, a collection should be 
unpacked and arranged by those who packed it originally. 
In collecting fossils, it is useless to take many specimens of one 
kind unless carriage is exceptionally plentiful. Two or three good 
examples of each kind are usually sufficient, but as many kinds as 
possible should be collected. Great care is necessary that all the 
