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LXXX. A Differ tation on the Antiquity of 
G/afs in Windows . In a Letter to the 
Rev . Tho. Birch, D. D. Secret . R.S. By 
the Rev . John Nixon, M. A. F. R.S. 
Dear Sir, London, March 2 . 1 75^* 
Read Mar. 2, nr Had the honour laft winter to lay before 
*75 8 - t } ie Royal Society a few obfervations 
upon fome of the curiofities found at Herculaneum, 
&c.{ 1 ). Among other articles, I juft mentioned a 
piece of a plate of white glafs ; and now beg leave 
to inquire into the ufes, to which fuch plates might 
be applied in the early age, to which this fragment 
undoubtedly belongs. 
And here a perfon, who forms his ideas of ancient 
cuftoms by what he lees praCtifed in latei dines, may 
be ready to offer feveral conjectures ; in fome Ox 
which he will, probably, be miftaken ; as in others 
he may be juftified by the genuine evidences of an- 
tiquity. ^ . . 
And, firft, It is obvious to imagine, . that lucn 
plates might ferve for fpecula , or looking-glades. 
And, indeed, that fpecula were anciently made, not 
only of metals, and fome ftones, as the ( 2 ) phengites, 
&c. but alfo of glafs, may, I think, be collected, 
from Pliny, who, having mentioned the city of Si- 
(1) In a paper read Feb. 24. 1757. See Art. xiii. p. 88. 
(2) Port'uuum , in quibus Jpatiari confueverat ( Domitianus) pa- 
rietes phengite lapide difinxit , e cujus fplendore per imagines quicquid 
a terzo fieret , providers. Sueton. Domit. c. 14. 
V o l. jo. 4 H don 
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