Undercut. A wall of a groove or recess which is sloping.

Undulatory. A wave-like motion, applied generally to light and electricity.

Unit. A base for calculating from.

Unison. Acting together; as one.

Unsized. Generally applied to the natural condition of paper or fabric which has no glue or other fixing substance on it.

Vaporising. To change from a liquid or solid to a gas.

Variation. Changing into different conditions; unlike forms.

Verge. The edge; usually applied to the shoulder of a watch spindle, particularly to the escapement.

Vertical. Up and down. The direction of a plumb line.

Velocity. The speed of an article through s.p.a.ce.

Vitascope. An instrument for determining the rate of vibration of different substances.

Vibration. The movement to and fro of all elements, and by means of which we are made sensitive of the different forces.

Vocation. The business or the calling of a person.

Warding. The act of cutting a projection or guard, such as is usually found on the insides of locks, and the correspondent detent in the key.

Watt. In electricity the unit of the rate of working in a circuit. It is the electro-motive force of one volt and the current intensity of one ampere.

BOYS' COPYRIGHTED BOOKS

Printed from large, clear type on a superior quality of paper, embellished with original ill.u.s.trations by eminent artists, and bound in a superior quality of book binders' cloth, ornamented with ill.u.s.trated covers, stamped in colors from unique and appropriate dies, each book wrapped in a glazed paper wrapper printed in colors.

MOTOR BOAT BOYS SERIES

By Louis Arundel

1. The Motor Club's Cruise Down the Mississippi; or, The Dash for Dixie.

2. The Motor Club on the St. Lawrence River; or, Adventures Among the Thousand Islands.

3. The Motor Club on the Great Lakes; or, Exploring the Mystic Isle of Mackinac.

4. Motor Boat Boys Among the Florida Keys; or, The Struggle for the Leadership.

5. Motor Boat Boys Down the Coast; or, Through Storm and Stress.

6. Motor Boat Boys' River Chase.

THE BIRD BOYS SERIES

By John Luther Langworthy

1. The Bird Boys; or, The Young Sky Pilots' First Air Voyage.

2. The Bird Boys on the Wing; or, Aeroplane Chums in the Tropics.

3. The Bird Boys Among the Clouds; or, Young Aviators in a Wreck.

4. Bird Boys' Flight; or, A Hydroplane Round-up.

5. Bird Boys' Aeroplane Wonder; or, Young Aviators on a Cattle Ranch.

CANOE AND CAMPFIRE SERIES

By St. George Rathborne

1. Canoe Mates in Canada; or, Three Boys Afloat on the Saskatchewan.

2. Young Fur Takers; or, Traps and Trails in the Wilderness.

3. The House Boat Boys; or, Drifting Down to the Sunny South.

4. Chums in Dixie; or, The Strange Cruise in the Motor Boat.

5. Camp Mates in Michigan; or, With Pack and Paddle in the Pine Woods.

6. Rocky Mountain Boys; or, Camping in the Big Game Country.

For sale by all booksellers, or sent postpaid on receipt of 75c

BOYS' COPYRIGHTED BOOKS

Printed from large, clear type on a superior quality of paper, embellished with original ill.u.s.trations by eminent artists, and bound in a superior quality of book binders' cloth, ornamented with ill.u.s.trated covers, stamped in colors from unique and appropriate dies, each book wrapped in a glazed paper wrapper printed in colors.

MOTOR BOAT BOYS SERIES

By Louis Arundel