384 DETERMINATION OF MINERALS. 



A mineralogist sometimes lias occasion to measure dis- 

 tances, 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 feet 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. ELEMEXTS. 



1. Lustre metallic ; liquid. 



2. Lustre metallic ; malleable and eminently sectile. 



3. Lustre metallic ; brittle ; B.B. on coal, wholly volatile, with no 



sulphurous fumes. 



4. Lustre metallic ; brittle ; H. =1-2 ; leaves a trace on paper ; B.B. 



on coal, infusible, no fumes or odor. 



5. Unmetallic ; burns readilv with a blue flame. 



6. Lustre adamantine ; H.="l0. 



