Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
Thereupon Caesar formed his plan. He ordered portable boats
of a light wooden frame and osier work lined with leather,
after the model of those used in the Channel among the Britons
and subsequently by the Saxons, to be prepared in the camp
and transported in waggons to the point where the bridges had stood.
On these frail barks the other bank was reached and, as it was found
unoccupied, the bridge was re-established without much difficulty;
the road in connection with it was thereupon quickly cleared,
and the eagerly-expected supplies were conveyed to the camp.
Caesar's happy idea thus rescued the army from the immense peril
in which it was placed. Then the cavalry of Caesar which in efficiency
far surpassed that of the enemy began at once to scour the country
on the left bank of the Sicoris; the most considerable
Spanish communities between the Pyrenees and the Ebro--Osca, Tarraco,
Dertosa, and others--nay, even several to the south of the Ebro,
passed over to Caesar's side.