Tin was employed by the ancients for mirrors: but mirrors of silver were gradually substituted; and these in Pliny’s time had become so common, that they were even employed by female servants or slaves.
That Pliny’s knowledge of the properties of tin was very limited, and far from accurate, is obvious from his assertion that _tin_ is less fusible than silver.[58] It is true that the ancients had no measure to determine the different degrees of heat; but as tin melts at a heat under redness, while silver requires a bright red heat to bring it into fusion, a single comparative trial would have shown him which was most fusible. This trial, it is obvious, had never been made by him.
The ancients seem to have been ignorant of the method of tinning iron. At least, no reference to _tin plate_ is made by Pliny, or by any other ancient author, that I have had an opportunity of consulting.
It would appear from Pliny, that both copper and brass were tinned by the Gauls at an early period. Tinned brass was called _æra coctilia_, and was so beautiful that it almost passed for silver. _Plating_ (or covering the metal with plates of silver), was gradually substituted for tinning; and finally _gilding_ took the place of plating. The trappings of horses, chariots, &c., were thus ornamented. Pliny nowhere gives a description of the process of plating; but there can be little doubt that it was similar to that at present practised. Gilding was accomplished by laying an amalgam of gold on the copper or brass, as at present.
7. Lead appears also to have been in common use among the Egyptians, at the time of Moses.[59] It was distinguished among the Romans by the name of _plumbum nigrum_. In Pliny’s time the lead-mines existed chiefly in Spain and Britain. In Britain lead was so abundant, that it was prohibited to extract above a certain quantity in a year. The mines lay on the surface of the earth. Derbyshire was the county in which lead ores were chiefly wrought by the Romans. The rich mines in the north of England seem to have been unknown to them.
Pliny was of opinion that if a lead-mine, after being exhausted, be shut up for some time, the ore will be again renewed.
In the time of Pliny leaden pipes were commonly used for conveying water. The vulgar notion that the ancients did not know that water will always rise in pipes as high as the source from which it proceeds, and that it was this ignorance which led to the formation of aqueducts, is quite unfounded. Nobody can read Pliny without seeing that this important fact was well known in his time.