216 



THE RANGE OF NATURE's OPERATIONS. 



There remains the ^o subsection, the subsection of smallest planet- 

 ary measures. These stand related to the other planetarj^ distances 

 in somewhat the same way as microscopical intervals are related to 

 other laboratory measures. The}' may be" called g-eographical inter- 

 vals, since in this subsection we measure the radii of the planets and 

 distances on their surfaces — quantities which can conveniently be 

 expressed as so many stages, each stage being 10 kilems (or 6i miles ^), 

 as shown in fig. 4. 



Fig. 4. 



Radii of planets, expressed in stages. 



[The subsection Bw provides for all of these.] 



GROUP B. 

 Planetaey Intervals. 



Bw 



Fig. 5. 



Examples of measured stellar distances, 

 expressed in metro-sixteeus. 



[The subsection Aw provides for all of these.] 



GROUP A. 

 Stellar Distances. 



A\\- 



000 



000 



One metro-sixteen, 



Distance at which par-) n i 



allax would be 1", / •^■' 



Distances of — 



rtCentauri 



61 Cygni 



Sirius 



o: Lvrje 1 



Limit of distancel 

 that can beascer-l.T 

 tained by paral-r' 

 lax J 



' I I 



GROUP A (stellar DISTANCES). 



The last group is that of stellar distances. These are most con- 

 veniently measured in metro-sixteens. 



The four units we have found it most convenient to use in dealing 

 with large magnitudes are very simply related to one another, as 

 appears from the following list of them: 



The unit we have found it convenient to use for geographical dis- 

 tances is the stage, the stage being a million of centimeters, or 10 

 kilems, or 6i miles. 



That IS, 61 metric miles. In science the mile of 1,600 meters, the furlong of 200 

 meters, the chain of 20 meters, and the perch or pole of 5 meters should always be 

 used instead of the so-called ' ' imperial ' ' measures of the same names. Here the old 

 or imperial measures are to the new or metric measures in the ratio of 100.582 to 100, 

 which is the same as the ratio of 172.8 to 171.8, between which last numbers the 

 amerence is 1. 



