triii D E D I C A T I O N .
It is to the fame goodnefs that I am
indebted for this opportunity of fubfcribing
myfelf,
S I R,
YOUR MAJESTY’S
Moft humble,
Molt obedient,
and molt dutiful
Subje£t and Servant,
GEORGE ADAMS.
P R E F A C E .
IN the preface to my E ssays on E lectricity and
Magnetism, I informed the public that it was my
intention to publifh, from time to time, elfays defcribing the con-
ftruftion and explaining the ufe of mathematical and philofophi-
cal inllruments, in their prefent Hate o f improvement. This
work will, I hope, be confidered as a performance o f my promile,
fo far as relates to the fubjeft here treated of.
The firll chapter contains a Ihort hiftory of the invention and
improvements that have been made on the microfcope, and
Father Torre s method o f making his celebrated glafs globules.
The fecond treats of vifion, in which I have endeavoured to explain,
in-a familiar manner, the reafon o f thofe advantages which
are obtained by the ufe of magnifying lenfes ; but as the reader is
fuppofed to be unacquainted with the elements of this-fcience, fo
many intermediate ideas have been neceflarily omitted, as mull
in fome degree lelfen the force, and weaken the perception of the
truths intended to be inculcated: to have given thefe would have
required a' treatife on optics.
b In