MOTHER-OF-PEABL 322 MOTION STUDY diet. The giant owl moth of Brazil measures nearly a foot from tip to tip, and there is a gilded species smaller than a pin's head. Certain moths are destitute of tongues and pass through the winged state without food. Among the moths notable for their striking ap- pearance, are the death's head, the luna (having long-tailed wings of light green), the royal walnut moth (exclu- sively American), the tiger and the sphinx moths. In their larval state, when they are known as caterpillars, moths are among the worst foes of our gardens, orchards and shade trees. The larva of the white miller is very common in gardens; the tent caterpillar is recognized by the webs it makes in fruit trees, and the larva of the apple moth (developed from eggs de- posited in the blossom end of the fruit) is very familiar. The household moths (Tmese) are well known on account of the injury they work among clothes, car- pets, furs, etc. One species of moth, the silk worm (Bombyx Mori) has long been serviceable to man. MOTHER-OF-PEARL, in zoology and commerce, the internal layer of oyster and other nacreous or pearly shells. In entomology, a moth of the family Botydse. MOTHERWELL, a city of Scotland in Lanarkshire, 12 miles S. E. of Glasgow. It has important iron and steel works, and there are large deposits of coal in the neighborhood. It has many important industrial establishments. Pop, about 40,000. MOTIF, a musical term meaning the principal theme on which the movement of a musical composition is constructed, and which, during the movement, is con- stantly appearing in one or other of the parts, either complete or modified. MOTION", a movement. In art, the change of place or position which from certain attitudes a figure seems to be making. In law, an application made to a court of justice by the parties to an action or their counsel, to obtain some rule of order of court necessary to the progress of the action. In music: (1) The movement of a single part with ref- erence to intervals taken by it. Conjunct motion takes place when the sounds move by single degrees of the scale, e. g., C. D, E, F; disjunct motion is when they move by skips, e. g., C, F, D, G. (2) The movement of two or more parts with relation to each other. Similar or direct motion is when parts move in the same direction either by single _ degrees or by skips; contrary motion is when parts move in opposite directions; oblique mo- tion is when one part remains stationary while another moves. In watches and clocks, the train of wheels immediately concerned in the moving of the hands. Organic molecular motion, a kind of motion occurring in nearly all the in- ternal processes in organic bodies. It must exist to produce absorption, secre- tion, etc. MOTION, LAWS OF, three principles or axioms which were laid down by Sir Isaac Newton: (1) If a body be started in motion, and if no force act upon it, that body will continue in motion in the same direction, and with the same velocity. Of course this cannot be directly proved by obser- vation, no one being able to start a body in a portion of the universe free from other bodies which will attract it, and if he could start it on in a vacant space, he coixld not watch its subsequent prog- ress through infinite space and eternity. But the length of time during which tops will spin or finely mounted pendulums will go in the exhausted receiver of an air pump, can be accounted for in no other way than by supposing the truth of the first law of motion. (2) Change of motion is proportioned to the acting force, and takes place in the direction of the straight line in which the force acts. (3) To every action there is always an equal and contrary reaction; or, the mu- tual actions of any two bodiesare always equal and oppositely directed in the same straight line. MOTION STUDY, a method employed by exponents of some of the many effi- ciency systems, now in existence, in which the motions which a worker makes in perfonning a routine operation are recorded and studied. A motion study of a process is usually made in conjunction with a time study of the same process. After the motions of several operatives doing the same work are recorded, a study is made and a process which is theoretically the best way of performing the given task is designed and given to the worker to follow. The early studies were made by means of a split second stop-watch, and a recording board. The modern method is to use a high-speed motion-picture camera, and include a large second-indicating clock in the pic- ture. When the film is slowly projected, it gives a complete and easily consulted record of the process. While great improvements in the methods of doing many processes have been made as a result of motion study,
