The army was now moving through the passes of the Pyrenees.

The labour was great; no army had ever before crossed this mountain barrier; roads had to be made, streams bridged, and rocks blasted away, to allow the passage of the elephants and baggage wagons.

Opinions have differed as to the explosives used by the Carthaginian miners, but it is certain that they possessed means of blasting rocks.

The engineers of Hannibal's force possessed an amount of knowledge and science vastly in excess of that attained by the Romans at that time, and during the campaign the latter frequently endeavoured, and sometimes with success, by promises of high rewards, to induce Hannibal's engineers to desert and take service with them.

A people well acquainted with the uses of sulphur and niter, skilled in the Oriental science of chemistry, capable of manufacturing Greek fire--a compound which would burn under water--may well have been acquainted with some mixture resembling gunpowder.
The art of making this explosive was certainly known to the Chinese in very remote ages, and the Phoenicians, whose galleys traversed the most distant seas to the east, may have acquired their knowledge from that people.
The wild tribes of the mountains harassed the army during this difficult march, and constant skirmishes went on between them and Hannibal's light armed troops.