146 
be divided. If it referred to 100 men instead of 1000, the 
ordinates would correspond to the 2nd, 9th, 25th, 50th, 75th, 
91st, and 98th men instead of the 20th, 90th, &c.; consequently 
the traveller need only deal with a moderate number of men, 
arranging* them in a series, and noting the height of those who 
stand at the quarter points. Thence he obtains c and r. He 
may do this for any quality whatever, running, shooting, 
colour, &c.; but it would be very proper that he should take 
notes concerning the men standing at the other points I have 
named, besides C and D. The common but much more labori¬ 
ous way of obtaining these results is to measure every individual 
and to group them into classes, so many per cent, between 5 feet 
1 inch and 5 feet 2 inches, so many between 5 feet 2 inches 
and 5 feet 3 inches, and so on, from which data c and r can be 
obtained by the ordinary tables. Always mention the number 
of people measured, for the reliability of the average depends 
upon it; it is, as already mentioned, as its square root. A 
good book on these matters has yet to be written. Quetelet’s 
letters on the Theory of Probabilities is perhaps the most suit¬ 
able to the non-mathematical reader; it is published in French 
in Brussels and is translated into English also (1849, Layton). 
THE END. 
Printed by Tayloe and Feancis, Red Lion Court, Fleet Street. 
