This work is and has been dedicated to a very honest man, born in Barcelona, but certainly unknown to the common world: he was either a man or an artisan or an engineer who worked hard in that town during the second half of the 15th century. His name was Bernat Vidal. As seen from this work, this personage enables us to go back to the Barcelona life of his time through the inventions he devised to improve the existing living conditions of the town. There were, amongst others, his ability to advance technically in making clocks and bells, patrol pumps, gunpowder, bombards and other war devices. He was also able to make devices to drain the Montjuic marshy region and build better water mills. Throughout this work, it may also be seen quite clearly his stubbornness and steadfastness to succeed in getting that such devices were fully applied for the intended uses and in overcoming the then existing lack of confidence of the town councils in their application.