207102An ESSAY
The firſt of theſe Machines is undoubtedly much
preferable to the other; becauſe it is firmer, and
renders the Work eaſier and exacter; and Prints may
be eaſier repreſented in it, than in the other. Add to
all this, that with a ſmall Alteration it may be made
capable of a few Uſes, which are peculiar to
the ſecond Machine; yet ſince this latter one is
much ſimpler, of a much leſs Price, and is eaſier to
be carry’d from Place to Place, I thought it conveni-
ent to lay down alſo its Deſcription in this ſmall
Tract.
preferable to the other; becauſe it is firmer, and
renders the Work eaſier and exacter; and Prints may
be eaſier repreſented in it, than in the other. Add to
all this, that with a ſmall Alteration it may be made
capable of a few Uſes, which are peculiar to
the ſecond Machine; yet ſince this latter one is
much ſimpler, of a much leſs Price, and is eaſier to
be carry’d from Place to Place, I thought it conveni-
ent to lay down alſo its Deſcription in this ſmall
Tract.
I ſhall not here take up the Reader’s Time in enu-
merating the Advantages accruing to Painters from
Machines of this Nature: But only add, that they
are of great Uſe for reducing or leſſening ſeveral ſe-
parate Objects in the ſame Picture; which therefore
may be copy’d after Nature in the moſt perfect man-
ner poſſible. It is very difficult to give ſeveral Objects
their true Bigneſs in a Picture, and to diſpoſe them
ſo as to have the ſame Point of Sight; but this is
done extremely eaſy by means of Machines; for the
Point of Sight in them will be the ſame always, as
long as the Convex Glaſs has the ſame Diſpoſition,
and the Bigneſs of the Repreſentations of Objects in
the Machines, do depend upon the Objects Diſtances
from them.
merating the Advantages accruing to Painters from
Machines of this Nature: But only add, that they
are of great Uſe for reducing or leſſening ſeveral ſe-
parate Objects in the ſame Picture; which therefore
may be copy’d after Nature in the moſt perfect man-
ner poſſible. It is very difficult to give ſeveral Objects
their true Bigneſs in a Picture, and to diſpoſe them
ſo as to have the ſame Point of Sight; but this is
done extremely eaſy by means of Machines; for the
Point of Sight in them will be the ſame always, as
long as the Convex Glaſs has the ſame Diſpoſition,
and the Bigneſs of the Repreſentations of Objects in
the Machines, do depend upon the Objects Diſtances
from them.
This Invention, by Induſtry, may be certainly im-
prov’d, and the following Obſervations will be not a
little conducing thereto. 1. You muſt uſe but one
Convex Glaſs; for when there are two or more, the
true Repreſentations of Objects will be loſt; which is
an Inconveniency one is alſo ſubject to, when a Con-
cave Glaſs is any ways us’d in the Conſtruction of the
Machine. 2. When more than two Mirrours or Look-
ing glaſſes are us’d, the Rays, after having ſuffer’d a
triple Reflection, are ſo weaken’d, that the Objects
will not be well repreſented: And even when but two
Mirrours are us’d, they muſt be well poliſh’d 3.
prov’d, and the following Obſervations will be not a
little conducing thereto. 1. You muſt uſe but one
Convex Glaſs; for when there are two or more, the
true Repreſentations of Objects will be loſt; which is
an Inconveniency one is alſo ſubject to, when a Con-
cave Glaſs is any ways us’d in the Conſtruction of the
Machine. 2. When more than two Mirrours or Look-
ing glaſſes are us’d, the Rays, after having ſuffer’d a
triple Reflection, are ſo weaken’d, that the Objects
will not be well repreſented: And even when but two
Mirrours are us’d, they muſt be well poliſh’d 3.
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