EECOLLECTIO.NS OF CHILDHOOD AND YOUTH. 7 



has become celebrated, 'Potash, which potash, then 

 potash, in short, which I now present to you.' 



The general principles which M. Dumas in his 

 teaching delighted to develop, the multitude of facts 

 which M. Balard unfolded to his pupils, all answered 

 to the needs of Pasteur's mind. If he loved the vaster 

 horizons of science, he was also possessed by the 

 anxious desire for exactitude, and for the perpetual 

 control of experiment. Each of the lectures of the 

 Ecole Normale and of the Sorbonne excited in him 

 a profound enthusiasm. One day M. Dumas, while 

 illustrating the solidification of carbonic acid, begged 

 for the loan of a handkerchief to receive the carbonic 

 acid snow. Pasteur rushed forward, and, presenting 

 his handkerchief, received the snow. He returned 

 triumphant, and running forthwith to the Ecole Nor- 

 male, repeated the principal experiments which the 

 illustrious chemist had just exhibited to his audience. 

 He preserved religiously the handkerchief which had 

 been touched by M. Dumas. 



Pasteur usually spent his Sundays with M. Bar- 

 ruel, the assistant of M. Dumas. He thought of 

 nothing but experiments. For a long time in one 

 of the laboratories of the Ecole Normale was exhibited 

 a basin perhaps it is still shown containing sixty 

 grammes of phosphorus obtained from bones bought 

 at the butcher's by Pasteur. These he had calcined, 

 submitted to the processes known to chemists, and 



