222 THE RANGE OF NATURE's OPERATIONS. 



celestial distances and fifthets of all periods of time. B}^ this means, 

 intervals which in nature have to be measured in Groups A and B of 

 figure 1 are represented on the model by the similarly situated measures 

 shifted one group to the right; i. e., the distances are to be read off in 

 Groups B and C instead of in Groups A and B. At the same time all 

 intervals of time and all velocities become on the model the fifthet, or 

 hundred-thousandth part, of what the}- are in nature, so that a celestial 

 velocity of so many kllems per second takes the form in the model of 

 a velocity of the same number of centimeters per second. 



The sun becomes a globe 14 centims (nearly 5i inches) across. Put- 

 ting this at the center, the earth is a grain of the smallest snipe shot 

 at the distance of 15 meters, attended bj^ the moon (a minute bead) 

 nearly 4 centims off; the whole solar system is comprised within a 

 sphere which- has a kilem for its diameter, and the distance upon the 

 same scale of the nearest star is 4,000 kilems (2,500 miles). 



A year is represented by 5i minutes (more exactly, 315.567 seconds), 

 in which time the grain of shot is to describe its revolution round the 

 sun; a day becomes 0.864 of a second, in which time the grain of shot 

 is to turn upon its axis. The earth's velocity in its orbit round the 

 Sun is nearly 30 kllems per second. This, upon the model, becomes 

 a speed of 30 centims, or 1 foot, per second; and if the grain of shot 

 travels along its orbit at this pace it will get round it in the 5i minutes 

 that represent a year. The relative velocity of the moon in its orbit 

 round the earth is nearly 1 kllem per second, so that the bead that 

 represents the moon is to advance along its little relative orbit, which 

 is about the size of the palm of one's hand, at the rate of 1 centimeter 

 per second. Upon the same scale, the velocity of light becomes a 

 speed of 3 kllems per second, which is more than twice the speed of 

 the swiftest projectiles of modern artillery. We are to imagine that 

 waves of telegraphy traveling at this high speed fill all the inter- 

 vening space and keep up a constant communication between the sev- 

 eral bodies of the standard model. 



It would be convenient if all astronomical diagrams were constructed 

 on scales which bear some simple relation to the standard model of the 

 heavens. This was attempted in the author's diagram of the orbit of 

 the November meteors (the Leonids), which has been copied into 

 many books on astronomy. It was intended that the diagram should 

 have been on a scale exactly one five thousandth part of the standard 

 model, l)ut as engraved it differs from the intended scale by about one- 

 thirtieth part. (See the Royal Dublin Society's journal for 1869, or 

 the Proceedings of the Royal Institution for 1879, in either of which 

 the original diagram will l)e found.) 



