These Spanish tribes were ever quarrelling, and knew, in Strabo's words, "no entertainment save in horsemanship and in the exercise of arms." Quantities of their weapons have been found all over Spain, such as the heads of spears and arrows, or the blades of daggers, hatchets, knives, and swords. With these Iberian tribesmen, as with other peoples of the ancient world, the truly prehistoric age is that of stone; hence they advanced to bronze, and finally to iron. Beuter, the historian of Valencia, wrote in 1534 that near to the town of Cariñena, in Aragon, on digging out some earthen mounds the excavators came upon enormous bones, flint lance and arrow heads, and knives the size of half an ordinary sword; all these in company with "many skulls transfixed by the said stones." In the collection at Madrid, formed by Don Emilio Rotondo y Nicolau, these primitive Spanish weapons number several thousands; and many more are in the National Museum.[102] [102] According to Tubino, the existence of a prehistoric age of stone was not suspected in Spain until the year 1755, when Mann y Mendoza affirmed that a state of society had existed in the Peninsula before the age of metals. Since then the Celtic remains of Spain and Portugal have been investigated by many scientists, including Assas, Mitjana, Murguía, and Casiano de Prado, who discovered numbers of these weapons. Towards the middle of last century Casiano de Prado, aided by the Frenchmen Verneuil and Lartet, explored the neighbourhood of San Isidro on the Manzanares, and found large quantities of arms and implements of stone. Valuable service in the cause of prehistoric Spanish archæology has also been performed by Vilanova, Torrubia, and Machado. Discoveries of ancient Spanish arms of bronze occur less often and in smaller quantities than those of stone or iron. Bronze hatchets, principally of the straight-edged class (_à bords droites_) have been found in Galicia and certain other provinces. Villa-amil y Castro describes a bronze dagger of curious workmanship, which was found in Galicia in 1869. The point of the blade is missing. If this were included, the length of the weapon would be about six inches. Other examples, now in the Madrid Museum, include two swords, two daggers, and two arrowheads. The swords, sharp-pointed, narrow in the blade, and used by preference for thrusting, were found not far from Calatayud--the ancient town renowned, as Roman Bilbilis, for weapons of incomparable temper. The daggers were probably used for fighting hand to hand.