19 
A. D . 165, all showing the presence of zinc in snfiicient quantity to 
constitute true brass; they also contained, in many instances, 
varying quantities of tin, iron, and lead. "When the brass coins 
contain a fair quantity of zinc their colour afiPords sufficient evidence 
of that metal to an experienced eye. The variety of colour Avhich 
shows itself in individual coins depends entirely upon the proportions 
in which the two metals are alloyed. If copper is alloj^ed with a 
small quantity of zinc the result exhibits a pale red or yellow red; 
a larger quantity makes it yellow, the colour being brightest when 
the two metals are in equal parts; with a still larger quantity of 
zinc it is white. An excess of this latter metal makes the alloy 
brittle; a small quantity of lead diminishes the ductility, and of 
tin increases the hardness. 
The following is an analysis of some of the coins. 
COIN OF 
COPPER. 
ZINC. 
TIN. 
IRON. 
LEAD. 
Trajan .... 
77-00 
21-00 
0-486 
0-374 
.... 
Vespasian . . . 
80-97 
18-48 
• « • • 
0-49 
Caracalla . . . 
74-24 
14-42 
5-28 
0-54 
Nero .... 
81-07 
17-81 
1-05 
.... 
• • • • 
Titus .... 
83-04 
15-84 
.... 
0-50 
• • 1 • 
Hadrian . . . 
85-87 
10-85 
1-14 
0-74 
1-73 
^ Faustina . . . 
79-14 
6-27 
4-97 
9-18 
May 4. — T. S. Noble, Esq., F. E. A. S., made some remarks on 
the astronomical works purchased by the Society. He said that 
English literature wds singularly deficient in works of this class, 
and that Bailly’s work appeared to have been the first complete 
History of Astronomy ever published. It was valuable as an 
attempt to trace the history of astronomy from the earliest time to 
the present era. Although much in this history respecting ancient 
astronomy must be considered more of a romance than a history, 
the account which Bailly gives of the progress of this science from 
the time of Hipparchus to recent times might be considered as 
reliable, and, on the whole, written in a spirit of fairness and justice. 
The four volumes forming this work were of special interest, as the 
books had evidently formed part of the library of the great French 
B 2 
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