556 



THE NATURE BOOK 



photographs. In others, which I have 

 purposely inckided — the function of zoo- 

 logical photogi^aphs being, in my judg- 

 ment, to afford a standard of recognition 

 — it is not so evident. Several causes may 

 account for its being badly defined. The 

 Adder may have an old skin (snakes 

 slough several times in the summer) ; 

 it may be a female or an old male — in 

 both cases the markings are obscured ; or, 

 it may be an example of melanism, which 

 is a comparatively common phenomenon 

 in Adders. 



In addition to the zigzag, Adders dis- 

 play a characteristic \'-marking on the 

 "nape" of the neck. It is irregular in 

 shape, but in one form or another it seems 

 to be invariable, and so challenges com- 

 parison with the V on immature Slow 

 Worms, which is also the fore- end of a 

 zigzag. 



To the observations (not my own) that 

 Adders produce about a dozen young at 

 fuU time, in membranous envelopes which 

 rupture at birth, and that the young are 

 six to eight inches in length. I ma}' perhaps 



be permitted to add my own answer to 

 the question — Does the Adder swallow 

 her young when danger threatens them, 

 and disgorge them when danger is past ? 

 This is a highly controversial subject, and 

 the state of the controversy may, I think, 

 be fairly summed up as follows : If the 

 question were at the present moment to 

 come before the courts, and there were 

 ranged on the one side scientific sceptics 

 who denied the possibility of the occur- 

 rence ; and, on the other side, behevers 

 (there are plenty of them, and honest 

 believers at that) ready to swear that they 

 had seen such an incident occur, and tliat 

 they could not have been mistaken, the 

 judge would be compelled to sum up 

 in fa\-our of the believers. Professor 

 Leighton has proved that the Adder's 

 gullet is sufficiently capacious to contain 

 the brood. He has not touched on the 

 scrimmage at the entrance, and it is the 

 consideration of this wliich compels me, 

 with aU reluctance, to range myself on the 

 side of the sceptics. 



Douglas English. 



THE STORY OF A SNOWFLAKE 



By J. LOMAS, F.G.S., A.R.C.S. 



OUT of doors the air is chilly and raw. 

 and the leaden sky promises an 

 early downfall of snow. We turn 

 indoors for comfort and warmth, and fall 

 to contemplation. The kettle is on the 

 hob, and from its spout dense clouds are 

 issuing. They are scarcely formed before 

 they evaporate and become in\isible. 



Without, snow has begun to descend, 

 first as tiny sparkling stars, then as 

 scattered flakes, and now large, curling, 

 downy flakes darken the air. What a 

 contrast within and without ! Yet when 

 we consider the two operations referred 

 to more closely we lind them to be related, 

 and that one is necessary to the other. 



The steam which has been dispersed 

 into the air of the room, though lost for 



a time to our senses, can be recovered. 

 Place a tumbler of cold water on the 

 table. The exterior gradual^ becomes 

 cUmmed, and in a little while drops of 

 water trickle down the sides. The fact 

 is, a certain volume of air is only cap- 

 able of dissolving a limited amount of 

 water vapour, and the quantity depends 

 upon the temperature. Cold air becomes 

 saturated with a small amount, while 

 warm air can hold more. So the cold 

 glass chilling the air immediately in con- 

 tact with it reduces the power to keep 

 the \-apour in the invisible state, and the 

 excess is deposited as tiny drops of liquid. 

 In place of the tumbler of water we may 

 substitute a \-essel filled with snow or, 

 stiD better, a mixture of snow and salt. 



