Dr. Pearson's Observations 
44 ° 
of tempering copper, which had been subsequently lost * If, 
instead of feigning such an hypothesis, these writers had exa- 
mined by analysis the ancient implements which fell under 
their observation, I cannot doubt that they would have unra- 
velled the mystery. Count Caylus himself had a glorious 
opportunity of ascertaining the composition of ancient copper 
instruments, when the seven swords, and hollow wheel were 
found at Genzac in 1751. If he had made but two adequate 
experiments, one to detect iron, and the other to detect tin, 
he would have had a much better foundation for reasoning 
than that of a mere hypothesis, however ingenious and 
learned.-f 
* “ It appears, says Dr. Lort,” in his paper upon celts, “ that the ancients had 
“ an art of tempering and hardening brass to a greater degree than is done at present, 
or perhaps than is necessary to be done.” Archaol. Vol. V. p. 187. 
With reluctance I must observe, that such an experienced inquirer as Dr. Priest- 
ley falls into the error of antiquaries, in asserting, that the ancients had a method, 
with which we are not w r ell acquainted, of giving copper a considerable degree of hard- 
ness, so that a sword might be made of it with a pretty good edge. But Pauw tells 
us, that the Americans were in possession of the secret of giving a temper to copper 
equal to steel. 
f At the desire of Count Caylus, the old metal instruments found at Genzac 
were examined by Geoffroy, the younger. To prevent all suspicion of this cele- 
brated chemist. being defrauded of the honour due to him by mistaking his meaning, I 
shall cite his own words. 
“ Je cherchai a m’assurer s’il y avoit dans ces armes antiques une portion d’etain 
“ sensible et aussi considerable que dans le metal que j’alliois. Pour cct effet je mis 
“ dans un bain de plomb sur une coupelle un petit morceau de mon alliage, qui 
“ aussi-tot qu’il commen5a a se fondre, vegeta, a cause de l’etain qu’il contenoit. J’ai 
“ repete cette experience, sur le metal des armes antiques, et ce metal n’ayant point ve- 
“ gete, mais etant plus difficile a fondre que le mien, je fus convaincu que ce n’etoit 
“ point l’etain qui durcissoit le cuivre, qui est le metal principal des jirmes.” 
This was the experiment for detecting tin ; and the following is the account of the 
vnethpds employed to determine the presence of iron. 
