SPREAD OF UNDERSTANDING 9 



Even a man like Leonardo da Vinci, endowed with so much 

 genius and originality, and who had himself dissected a large num- 

 ber of bodies and examined very minutely many a heart, even he 

 was subjugated by this intangible dogma. This is the more pa- 

 thetic in that Leonardo was certainly on the scent of the true ex- 

 planation, but the invisible holes were too sacred to be touched, 

 and nothing but this prejudice caused his failure to discover and 

 to proclaim the circulation of the blood. 



When I shut my eyes and evoke the past, I imagine that this 

 great discovery was enclosed in a chest of which intelligent ob- 

 servers like Leonardo, Vesalius, Servetus or Columbus could have 

 easily found the secret if they had set their hearts upon it, but they 

 did not dare approach near enough because Prejudice sat on the 

 lid. I can see those great men standing shyly around the coffer, 

 mysteriously attracted by it, yet awed into impotence, while Truth 

 was prisoner inside. 



A moment of reflection will now convince you that the second 

 story is not so widely different from the first as it might appear at 

 first view. In both cases the application of a great discovery was 

 delayed for more than a millennium by unreasonable prejudices. 

 But in the first case the obstruction occurred after the discovery 

 and prevented it from becoming effective, while in the second, 

 prejudice blocked the way to the discovery itself, preventing it 

 from being made. 



7he Jhird Story (which is in some way a secjuel to the first). 

 Prince Maurice of Nassau, stathouder of the Low Countries, took 

 into his service about the year 1593 a Fleming of considerable 

 genius, Simon Stevin of Bruges. He used to refer to him for mathe- 

 matical advice and employed him as his chief hydraulic engineer 

 and as quartermaster general of his armies. This Stevin has not 

 yet received his full meed of recognition, for he certainly was one 

 of the greatest men of the sixteenth century. Various important 

 discoveries or inventions are ascribed to him and the historian of 

 mechanics can quote no greater name for the whole interval (of 



