114 



THE GUIDE TO NATURE 



combination two molecules of water 

 and has the composition represented 

 by the formula NaC1.2HoO. On fur- 

 ther cooling of the solution the solu- 

 bility of the hydrated salt, NaC1.2H20, 

 changes along the line CB and finally 

 terminates at the cryohydric point B, 

 corresponding to a concentration of 30 

 grams of sodium chloride per 100 

 grams of water. This diagram makes 

 it clear that the most economic pro- 

 portion in which to mix ice and salt 

 for the production of low temperatures 

 is that corresponding to the composi- 

 tion of the cryohydrate. 



It is obvious from the foregoing dis- 

 cussion of the mechanism of the pro- 

 duction of low temperatures by means 

 of ice and salt, that the function of salt 

 in removing ice from a side-walk in 

 winter is to form a salt solution having 

 a lower freezing point, the changes in- 

 volved represented by the line AB. 



The Snail. 



BY ROBERT S. WALKER, CHATTANOOGA, 

 TENNESSEE. 



Almost everyone knows a snail when 

 he sees one. but how much do we know 

 about the queer, interesting little crea- 



PEACHES EATEN BY SNAILS. 



ture? To begin with, did you suppose 

 there were more than fifty difi:'erent 

 kinds of snails in the United States? 

 There are, although by far the most com- 

 mon is the Helix Pennsylvanica. 



A good many people believe that snails 

 are blind ; they are not, although their 

 sight is not at all keen. If you watch a 

 snail moving about, you will see it push 

 out its two tentacles, which remind us of 

 the antennse of a butterfly. The eyes arc 

 placed at the tips of these tentacles. 



How and when does the snail Sfet his 



shell? That is another question often 

 asked by country folk. The answer is : 

 he is born with it. The eggs are laid in 

 early spring, and within four weeks they 

 hatch. The eggs are enclosed in a cap- 

 sule, and an amazing number of little 

 snails, usually about fifty, each in its deli- 

 cate shell, are to be found in each cap- 

 sule. The shell hardens rapidly as it is 

 exposed to the air, and the snail soon is 

 ready for business. 



Never look for a snail in a sunny, dry 

 spot. Go to the cool, shady, grassy side 

 of the house or garden, and if there are 

 snails about you will find them. Violet 

 beds are their favorite places of abode. 

 They eat almost any kind of green thing. 

 If you wish to give the snail a particular 

 treat, scatter a few peaches in the grass 

 plot or on the border of the violet bed. 

 You may have a hundred snails in such 

 a bed and never know it until you have 

 tried the peach test. By the second morn- 

 ins^ you may find that the snails have 

 visited every peach and eaten most of 

 them. Snails break the skin of a peach 

 and eat directly to the seed, and then 

 continue to eat until nothing remains 

 but a clean seed and a thin, fuzzy peach 

 skin. Sometimes you will find as many 

 as four snails wrestling with a single 

 peach. Snails do not have teeth. The 

 mouth is only a slender rasp-like "Ungual 

 ribbon." 



A shower of rain is bn.lm to a snail. 

 That tender body of his must secrete 

 plenty of mucus or oil, so there will be 

 no friction and no sore feet when the 

 day's journey is over. So dry weather 

 is hard on the snail. A parched atmos- 

 nhere absorbs much of the precious mois- 

 ture that he cannot afford to lose. But 

 when the misty days occur he is out im- 

 mediately, tossing out his tentacles as if 

 testing the humidity of the atmosohere, 

 and usins: them as a nearsighted person 

 uses a cane. The snail can walk only about 

 twelve feet an hour, but he can walk 

 up a pane of glass as fast as he can alono" 

 a level garden nath. That is because his 

 creeping foot secretes a constant supply 

 of mucus, and the contact of the foot is 

 always with the surface of mucus and 

 not with the elass or the eround. What- 

 ever the surface or the slone of his track, 

 the friction aeainst which the snail must 

 contend is always exactly the same — 

 The Youth's Companion. 



