TECHNICAL INDEX AND GLOSSARY 



proved by Robert Hooks, and finally brought to its present state 

 of perfection by the efforts of Sir David Brewster, Dr. Wollas- 

 ton, Coddington, and Joseph Jackson Lister. See "Lister and 

 the Perfected Microscope," Vol. IV, p. 109. 



Milky Way. A luminous band in the heavens, composed of 

 stars and nebulae. This fact was discovered by Galileo with the 

 telescope which he invented. See Vol. II, p. 79; and the general 

 treatment of modern astronomy, "The Progress of Modern 

 Astronomy," Vol. Ill, p. 19. 



Molecule. The smallest mass of any substance that can exist 

 in a separate form. The atom is, of course, smaller, but single 

 atoms cannot exist alone. See "The Ether and Ponderable 

 Matter," Vol. Ill, p. 283. 



Monorail Systems. Railways having a single rail, on which 

 cars with double-flanged wheels are kept in a state of equilibrium 

 either by overhead supports, or by means of a gyroscope. The 

 Gyrocar (q.v.) of Louis Brennan is an example of this latter 

 type. See "The Gyrocar," Vol. VII, p. 195; and "Monorail Sys- 

 tems," Vol. VII, p. 191. 



Moon's Variation, which was discovered by an Arabian astron- 

 omer about 975, is the inequality of motion of the moon, in 

 virtue of which it moves quickest when new or full, and slowest 

 at first and third quarter. Later (about 1750) this fact was re- 

 discovered by Tycho Brahe. For modern studies of the moon, 

 see "Studies of the Moon," Vol. Ill, p. 48. 



"Mule." A spinning machine invented by Samuel Crompton 

 about 1779. As it was a combination of the spinning-jenny and 

 Arkwright's drawing-rollers a hybrid machine it was dubbed 

 "mule," after that hybrid animal. See "The Invention of the 

 'Mule,' " Vol. IX, p. 32. 



Multiple Messages. In telegraphy it is possible to send 

 several messages at the same time in opposite directions over 

 a single wire. The first machine for doing this was invented 

 by an Austrian, Dr. Gintl, in 1853. See "Multiple Messages," 

 Vol. VIII, p. 25. 



Muscles. A kind of animal tissue capable of contracting in 

 length and dilating in breadth. The voluntary muscles, as the 

 biceps of the arm, are under control of the will, while the in- 

 voluntary muscles, such as those of the heart, intestines, etc., 

 are not. All muscles respond to electrical stimuli. See "The 

 Animal Machine," Vol. VI, p. 43. 



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