158 RIVEEBY 



often preserve and renew the past for him in this 

 way. 



These leaves from my own journal are not very 

 good samples of this sort of thing, but they preserve 

 for me the image of many a day which memory alone 

 could never have kept. 



March 3, 1879. The sun is getting strong, but 

 winter still holds his own. No hint of spring in the 

 earth or air. No sparrow or sparrow song yet. But 

 on the 5th there was a hint of spring. The day 

 warm and the snow melting. The first bluebird 

 note this morning. How sweetly it dropped down 

 from the blue overhead ! 



March 10. A real spring day at last, and a rouser ! 

 Thermometer between fifty and sixty degrees in the 

 coolest spot; bees very. lively about the hive, and 

 working on the sawdust in the wood-yard; how 

 they dig and wallow in the woody meal, apparently 

 squeezing it as if forcing it to yield up something to 

 them! Here they get their first substitute for pol- 

 len. The sawdust of hickory and maple is preferred. 

 The inner milky substance between the bark and 

 the wood, called the cambium layer, is probably the 

 source of their supplies. 



In the growing tree it is in this layer or secretion 

 that the vital processes are the most active and po- 

 tent. It has been found by experiment that this 

 tender, milky substance is capable of exerting a very 

 great force ; a growing tree exerts a lifting and push- 

 ing force of more than thirty pounds to the square 

 inch, and the force is thought to reside in the soft 



