1868. | The Past and Present of Chemistry. 23 
upon their physical properties, was the natural consequence of the 
slight knowledge of chemical qualities which the ancients possessed. 
The idea of chemical composition had not yet been conceived ex- 
cept, perhaps, in its very crudest form, as suggested by the com- 
position of metallic alloys artificially prepared. But the well-known 
metals were scarcely distinguished from each other ; thus lead and 
tin were regarded by the Romans as differently coloured varieties 
of the same metal—as dark and light lead. Of the most important 
chemical problems, such as those relating to combustion, to the 
changes effected in metals by the action of fire, or the caustic qualities 
of quicklime, we find scarcely a single one proposed, still less any 
attempts made at their solution. In regard to their knowledge of 
chemistry the ancients may be compared to ignorant or half-educated 
tribes of the present age; knowledge of important chemical pheno- 
mena they did not lack, but they made no attempt whatever to 
discover the causes of these phenomena. 
This almost total ignorance on the part of the ancients, espe- 
cially the Greeks, of any of the aspects of chemistry, is due entirely 
to their method of scientific investigation. Chemistry is essen- 
tially an experimental science, but experimental methods were little 
known either to the Greeks or Romans. The favourite mode of 
investigation with the most highly-cultivated people of antiquity, 
consisted in attempts to attain, by a pure effort of the intellect, to 
the conception of an universal principle by means of which all 
phenomena might be predicted and explained. Such a method of 
research could not even enable them to approach the domain of 
a science like chemistry. A few centuries later, however, we find 
the art of experimenting more advanced, and a real, if somewhat 
vague attempt being made to obtain a knowledge of the chemical 
composition of at least one class of bodies. It is true that this 
knowledge was sought after, not for its own sake, but as an aid to 
the solution of the problem of the transmutation of the common 
into the nobler metals. Alchemy existed in the fourth century of 
our era, and for more than a thousand years presented almost the 
only, and certainly the most important field for the development 
of chemistry. 
Our knowledge of the spread of alchemy, and of the resulting 
progress of chemistry, is very defective for the period between the 
fourth and the thirteenth centuries, and we know nothing whatever 
of the origin of alchemy, nor where it was first attempted. All 
that can with certainty be said is, that alchemy is undoubtedly older 
than the most ancient testimony that has reached us concerning 
it (from the fourth century), for this testimony does not speak of it 
as a new pursuit but as one which had long been carried on. The 
confident assertions regarding the practicability of alchemy do not 
now concern us, but it is important to a clear comprehension of the 
