24 HOUSE, GARDEN, AND FIELD 



and unmistakeable distinction between running and walk- 

 ing ? Why do horses and cows drink as human beings 

 do, by sucking in the water ; whereas dogs and cats drink 

 by lapping ? What is the adjustment of the parts of the 

 eye which gives the infantine stare, as contrasted with 

 that adjustment which gives the calm gaze of the adult ? 

 What advantage does a plant get from having a hollow 

 stem or stem filled with pith ? and why is this advantage, 

 which many short-lived plants avail themselves of, un- 

 available by trees, save when young and afterwards in 

 their shoots ? Why, in a river, is the water next a convex 

 shore usually shallow, and the bottom often sandy ? 



" A teacher who understood his business would be con- 

 tinually devising questions of these and countless other 

 kinds, to which no answers could be found in books, and 

 would persistently refuse to give the answers : leaving 

 the questions to be puzzled over for years if need were. 

 The mental exercise which solving one such question 

 implies, is of more value than that implied by a dozen 

 rote-learnt lessons." l 



VII. HONEY-DEW. 



All through the summer, when the weather is warm 

 and dry, honey-dew may be seen on the leaves of the 

 sycamore-maple. Sometimes it is found on bushes which 

 are overhung by sycamores, and in a city the pavement 

 under a sycamore may be seen to be spotted with drops 

 or patches of the same kind. If you are able to use the 

 tests for sugar, it is worth while to sponge the leaves or 

 pavements, then to squeeze out a little liquid from the 

 wet sponge, and satisfy yourself that it really does contain 

 sugar. Naturalists of old times judged by the taste, 

 found it sweet, and concluded that the honey fell from 

 heaven, or was exhaled from plants. The first serious 



1 Autobiography, vol. ii. p. 321. 



