Full text: Gravesande, Willem Jacob: An essay on perspective

An ESSAY on out the Camera Obſcura, is ſimilar to that which
they form, after having paſſed through the Glaſs: Therefore the Rays which fall upon the Paper in
the Camera Obſcura, likewiſe give the true Re-
preſentation of the Objects thereon. Which was
to be demouſtrated.

Theſe Objects appear inverted, becauſe the
Rays croſs each other in paſſing through the Glaſs; thoſe coming from above going below, & c.

199. Theorem II.

3. The Reflection which the Rays of Light ſuffer
upon a plain Mirrour or Speculum, before they fall
upon a Convex Glaſs, no-wiſe deforms the Repreſen-
tation of Objects.

This is evident: For the Speculum reflects the
Rays in the ſame Order as it receives them.

Now to ſhew the Uſe that may be drawn from
the Camera Obſcura in Deſigning, I ſhall here lay
down the Deſcription and Uſe of Two Machines,
which I uſe for this End.

200. The Deſcription of the Firſt Machine.

4. This Machine is ſomething in Figure of a
Chair, (ſuch as People are carried in) the back Part
of the Top is rounded, and its Foreſide P Q ſwells
out in the middle: Vide Fig. 70. which repreſents
the Machine, the Side whereof oppoſite to the
Door, is ſuppoſed to be raiſed up, that ſo its In-
ſide may be ſeen.

200.1.

Fig. 70.

5. The Board A within-ſide, ſerves as a Ta-
ble, and turns upon two Iron-pins, going into
the Wood of the Fore-ſide of the Machine, and is
ſuſtain’d by two ſmall Chains, that ſo the ſaid
Table may be lifted up; and therefore one may

Note to user

Dear user,

In response to current developments in the web technology used by the Goobi viewer, the software no longer supports your browser.

Please use one of the following browsers to display this page correctly.

Thank you.

powered by Goobi viewer