Eretria, like its neighbour Chalcis, early entered upon a commercial and colonizing career.
In 1526 he was sent out in command of an expedition fitted out for the purpose of determining by astronomical observations the exact line of demarcation, under the treaty of Tordesillas, between the colonizing spheres of Spain and Portugal, and of conveying settlers to the Moluccas.
Finding their comrades did not return, Irala and his companions determined to descend the river, and on their downward journey opposite the mouth of the river Pilcomayo, finding a suitable site for colonizing, they founded (1536) what proved to be the first permanent Spanish settlement in the interior of South America, the future city of Asuncion (15th August 1536).
Baron Hirsch (q.v.) founded the Jewish colonial association, which has undertaken vast colonizing and educational enterprises, especially in Argentina, and more recently the Jewish territorial organization has been started to found a home for the oppressed Jews of Russia.
His colonizing system was exposed to very severe criticism, yet it is impossible not to admire the results of his stupendous activity.