48 PRESIDENT’S ADDRESS—SECTION B. 
Before Aristotle’s time Thales (B.c. 600) had proved by similar 
methods of reasoning that water was the original element out of 
which all matter was produced. 
This position was assigned to air by Anaximenes (550 B.c.), 
and Heraclitus (B.c. 500) announced that fire was the original 
element. How strong a hold these teachings had is shown by the 
fact that up to quite recent times (1661) this was the universally 
received conception of the elements, and that our language still 
contains tracings of these teachings in such expressions as 
watery element, fiery element, and so forth. 
The Greeks passed on their chemical knowledge to their 
Roman conquerors. If we take Pliny the elder (died 79 a.p.), as 
our authority as to the condition of chemical technology in his 
time, we find a very considerable progress in chemical know- 
ledge. Of metals they knew at least seven which they were 
able to prepare, some in a state of considerable purity. They 
knew also many alloys, bronzes, brass, &c., and used a gold and 
mercury amalgam for gilding. 
Many metallic salts were known and used as medicines, such 
as common salt, sulphate of iron, nitre, salammoniac, alum, &c. 
Sulphur was used in bleaching wool. Even a number of organic 
substances were known—acetic acid (the only acid known), 
soaps, fats, and the combination with lead (our lead-plaster), 
sugar, starch (already prepared on the large scale). They used 
soda and some basis in dyeing. Of dye-stuffs, the most impor- 
tant were the purple of the murex (Tyrian) and indigo. 
With the fall of Rome, Byzantium became the seat of Roman 
learning, the Byzantine philosophers being in close touch with 
Alexandria, and it is in Alexandria more particularly that we 
find the headquarters of scientific thought up to the 7th century. 
To the Alexandrines we owe, especially, many strictly chemi- 
cal operations in use in our laboratories to the present day, such 
as distillation, filtration, &c. With the prominence of the 
Alexandrine school begins a new and remarkable era in the 
history of chemistry, namely, the period of alchemy. 
ALCHEMY. 
The object of chemistry during this long period, which lasted 
from the middle of the 7th century till the 16th century, was 
simply to convert baser metals into gold. The idea of the tran- 
substantiation of metals was not unknown to the Greeks, but 
appears to have made little headway with them. 
It became the leading object of the Egyptian chemists of 
Alexandria, and in the 7th and 8th centuries the Arabian con- 
querors gave it special prominence, and by them it was intro- 
duced through Spain into Western Europe. 
