384 DETERMINATION OF MINERALS. 
A mineralogist sometimes has occasion to measure dis- 
tauces, and by the following method he may make himself 
quite an accurate odometer : 
Let him first find, or make, along a roadside, a measured 
distance of 800 to 1, 000 feet, and then walk it at his ordi- 
nary walking pace three or four times, and note the number 
of steps. He will thus ascertain the actual length of his 
pace, and also find that in his ordinary walk it does not 
differ much from thirty inches ; it may be an inch or two 
less, or one, two, or three more than this. Now four times 
thirty inches is ten feet. If then, as he walks, he counts 
one for every fourth step, each unit in the count will stand 
for ten fect nearly, and 100, for 1,000 feet nearly. If his 
pace is thirty-one inches, let him add a unit for every 
thirty in the counting, or, which is the same thing, call his 
thirty thirty-one, and the needed correction will be made; 
or if his step is twenty-nine and one-half inches, subtract 
one from every sixty in the counting, or in other words du- 
plicate the sixty. Or the correction may be made at the 
end of the pacing ; if at 600, this number, after adding 
a thirtieth, becomes 620; and the distance would hence be 
6,200 feet. With a little practice the counting may be 
carried on almost unconsciously, and when the “thoughts 
are elsewhere; that is, unless there is a talking friend by 
one's side. 
An instrument, called a pedometer, of the shape and size 
of a small watch, is to be had of instrument makers, which, 
if carried in the waistcoat pocket, will do the registering for 
the pedestrian and note the distance, without any attention 
on his part. But the odometer explained above, when once 
in working order, is always at hand. 
SYNOPSIS OF THE ARRANGEMENT. 
I. ELEMENTS. 
. Lustre metallic ; liquid. 
. Lustre metallic ; malleable and eminently sectile. 
Lustre metallic ; brittle ; B.B. on coal, wholly volatile, with ne 
sulpburous fumes. 
. Lustre metallic ; brittle ; H.=1-2; leaves a trace on paper ; B.B. 
on coal, infusible, no fumes or odor. 
. Unmetallic : burns readily with a blue flame. 
. Lustre adamantine ; H.=10. 
aot - w~H 
