t two and a half inches in diameter, but the size
is of little consequence. The main conditions are to keep the light well
to one side, that no direct rays pass through the lens to illuminate the
screen, and to concentrate as bright a light as possible on the picture,
and on that alone. There should be no other light in the room when the
experiment is tried, and the picture should be very clear and distinct.
Two double convex lenses placed one at each end of a tube of card-board
will act better than one lens alone.

ADVERTISEMENTS.

HARPER'S YOUNG PEOPLE.

HARPER'S YOUNG PEOPLE will be issued every Tuesday, and may be had at
the following rates--_payable in advance, postage free_:

SINGLE COPIES $0.04
ONE SUBSCRIPTION, _one year_ 1.50
FIVE SUBSCRIPTIONS, _one year_ 7.00

Subscriptions may begin with any Number. When no time is specified, it
will be understood that the subscriber desires to commence with the
Number issued after the receipt of order.

Remittances should be made by POST-OFFICE MONEY ORDER or DRAFT, to avoid
risk of loss.

ADVERTISING.

The extent and character of the circulation of HARPER'S YOUNG PEOPLE
will render it a first-class medium for advertising. A limited number of
approved advertisements will be inserted on two inside pages at 75 cents
per line.

Address
HARPER & BROTHERS,
Franklin Square, N. Y.

CANDY

Send one, two, three, or five dollars for a sample box, by express, of
the best Candies in America, put up elegantly and strictly pure. Refers
to all Chicago. Address

C. F. GUNTHER,
Confectioner,
78 MADISON STREET, CHICAGO.

=KEEP YOUR BIRD= IN HEALTH AND SONG by using =SINGER'S PATENT GRAVEL
PAPER=. Sold by Druggists and Bird Dealers.

Depot, 582 Hudson St., N. Y.

FOR 1880. JUST OUT.

[Illustration: SPALDING'S BASE BALL GUIDE]

The highest authority on Base Ball. The only book published containing
the official =League Playing Rules=, under which every club in America
plays; also players' averages, illustrations on curve pitching, batting,
&c. Every lover of base ball should have a copy. Mailed, postpaid, upon
receipt of 10c. =A. G. SPALDING & BROS., Publishers, Chicago, Ill.=

OUR CHILDREN'S SONGS.

* * * * *

Our Children's Songs. Illustrated. 8vo, Ornamental Cover, $1.00.

* * * * *

The best compilation of songs f