L60 THE FORMS OF WATER IN 



shifting of the point of maximum motion from side to 

 side across tne axis of the glacier (§ 25). 



402. It is right that you should know that scientific 

 men do not always agree in their estimates of the com- 

 parative value of facts and ideas ; and it is especially 

 right that you should know that your present tutor 

 attaches a very high value to ideas when they spring 

 from the profound and persistent pondering of superior 

 minds, and are not, as is too often the case, thrown out 

 without the warrant of either deep thought or natural 

 capacity. It is because I believe Eer lu's labours fulfil 

 this condition, that I ascribe to then so high a value. 

 But when you become older and be cter informed, you 

 may differ from me ; and I write tJ .ese words lest you 

 should too readily accept my opinion of Rendu. Judge 

 me, if you care to do so, when your knowledge is 

 matured. I certainly shall not fear your verdict. 



403. But, much as I prize the prompting idea, and 

 thoroughly as I believe that often in it the force of 

 genius mainly lies, it would, in my opinion, be an error 

 of omission of the gravest kind, and which, if habitual, 

 would ensure the ultimate decay of natural knowledge, 

 to neglect verifying our ideas, and giving them outward 

 reality and substance when the means of doing so are 

 at hand. In science thought, as far as possible, ought 

 to be wedded to fact. This was attempted by Rendu, 

 and in great part accomplished by Agassiz and Forbes. 



