SIMON STEVIN 21 



and he found laws of their action and connection of the most 

 general importance; and from these he proceeded to advance 

 very much further. 



He began as tax-collector in his native town of Bruges, but 

 left this activity already at the age of 23 years, and then 

 travelled through Germany, Poland, and Sweden, and also 

 studied at the University of Leyden. His extraordinary 

 power of dealing with mechanical questions resulted finally 

 in his becoming controller of the land and water construction 

 of Holland, and quartermaster-general of the Dutch army. 

 Departing from the usual custom of the time, he published 

 his scientific studies not in Latin, but in his native tongue, 

 Dutch; and they were then translated into other languages. 



His main approach to the doctrine of the equilibrium of 

 forces (statics), which he brought to perfection in all funda- 

 mental points, was the inclined plane. The picture of the 

 triangular inclined plane standing upon a horizontal base, 

 with the endless chain around it, is found on the cover of 

 one of his chief works, with the inscription 'Wonder en is 

 gheen wonder' (A marvel and yet no marvel). The marvel 

 in this case is the simplicity of the rule, that the ratio of 

 reduction in force on the inclined plane is equal to the ratio 

 of the height to the length of the plane. It is shown that 

 this law is not a marvel; for it is proved to follow from the 

 fact, which appears to us as self-evident, that the endless 

 chain in question would never of itself start to slide on the 

 plane by virtue of its own weight, however frictionless the 

 contact might be. Stevin exhibited for the first time, in a 

 fully worked out and important example, a mental experi- 

 ment; that is to say, an experiment which does not need to 

 be carried out in reality, since the result of it is already 

 sufficiently in our possession, and hence already available 

 in consciousness. The chain will not start to move. For 

 if it did so, it would have to continue to move indefinitely, 

 since in either direction of motion the same distribution of 



