746 KANSAS CITY REVIEW OF SCIENCE. 
meteorites, all move in grand march toward the constellation, Hercules. The 
‘entire Universe is in motion. But these revelations of the micrometer are tame 
compared with its final achievement, the discovery of parallax. 
This means difference of direction, and the parallax of a star, is the differ- 
ence of its direction when viewed at intervals of six months. Astronomers 
observe a star to-day with a powerful telescope and micrometer; andin six months 
again measure the same star. But meanwhile the earth has moved 183,000,000 
miles to the east, so that if the star has changed place, this enormous journey 
caused it, and the change equals a line 91,400,000 miles long as viewed from the 
star. For years many such observations were made; but behold the star was al- 
ways in the same place; the whole distance of the sun having dwindled down to 
the diameter of a pin point in comparison with the awful chasm separating us from 
the stars. Finally micrometers were made that measured lines requiring 100,000 
to make an inch; and a new series of observations begun, crowning the labors of 
a century with success. Finite man actually told the distance of the starry hosts 
and gauged the universe. 
When the parallax of any object is found, its Liaiseanes is at once known, for 
the parallax is an arc of a circle whose radius is the distance. -By an important 
theorem in geometry it is learned, that when anything subtends an angle of r’ its 
distance is 206,265 times its own diameter. The greatest parallax of any star is 
that of Alpha Centauri— 2, of a second; henceit is more than 206,265 times 91, - 
400,000 miles—the distance of the sun—away, or twenty thousand billions of 
miles. This is the distance of the nearest fixed star, and is used as a standard of 
reference in describing greater depths of space. ‘This is not all the micrometer 
enables man to know. When the distance separating the earth from two celestial 
bodies that revolve is learned, the distance between the two orbs becomes known. 
Then the period of revolution is learned from observation, and having the distance 
‘and time, then their velocity can be determined. The distance and velocity being 
given, then the combined weights of both suns can be calculated, since by the 
laws of gravity and motion it is known how much weight is required to produce 
so much motion in so much time, at so much distance, and thus man weighs the 
stars. If the density of these bodies could be ascertained, their diameters and 
volumes would be known, and the size of the fixed stars would have been meas- 
ured. Density can never be exactly learned; but strange to say, photometers 
measure the quantity of light that any bright body emits; hence the stars cannot 
have specific gravity very far different from that of the sun, since they send simi- 
lar light, and in quantity obeying the law wherein light varies inversely as the 
squares of distance. Therefore, knowing the weight and having close approxima- 
tion to density, the sizes of the stars are nearly calculated. The conclusion is now 
made that all suns within the visible universe, are neither very many times larger 
nor smaller than our own. (Newcomb and Holden’s Astronomy, p. 454). 
Another result followed the use of the micrometer; the detection of the 
proper motion of the stars. For several thousand years the stars have been 
