16 THE NATURE-STUDY REVIEW [6:i-Jan., i9io 



We now have evidence that their immunity is due to other 

 causes. 



Chemical action is the most common cause of heat. The 

 action of Hme and water may be cited as one among a hundred 

 ilkistrations. Both may be cold to begin with but a tempera- 

 ture as high as boiling water is soon reached. If we use a 

 large quantity of lime and the appropriate amount of water, 

 the heat produced will set fire to wood. The large quantity 

 serves two purposes; i, it produces more chemical action and 

 hence more heat; and 2, it covers and prevents the loss of heat. 

 The reasons for taking only the appropriate amount of water 

 are, i, if we take too little the action will not produce heat 

 enough; and 2, if we take too much the heat will be dissipated 

 by warming and evaporating the extra water. When the prop- 

 er amount is taken no water is left. The mass is absolutely dry, 

 all the water having been changed chemically into something 

 else. 



When we cover ourselves with so-called warm blankets 

 we do not produce heat thereby, but we prevent the loss of that 

 which is produced. It is not possible for us to increase our 

 bodily temperature much by covering, since this merely re- 

 strains the life process which produce the heat. On the other 

 hand we may accustom ourselves to go with little clothing, 

 even in winter, and our bodies, Hke automatic machines, keep 

 up the normal body temperature by producing more heat. 



Many experiences impress upon us the fact that chemical 

 action produces heat. My next study would lead us to the 

 furnace and the boiler. 



A RECORD OF SOME STUDIES IN MAGNETISM 



By JESSIE R. MANN, Assistant in Science, Northern Illinois State Normal 

 School, Dekalb, III. 



The subject of magnetism is a very old one to the text- 

 books but a rather new one to the nature-study course. It has 

 proved a very interesting subject to a class of thirty-four 

 pupils, twelve boys and twenty-two girls, who have just com- 

 pleted the eighth grade in country schools. 



In performing the simple experiments, the children have 

 worked in groups of four except in a few cases where the 

 teacher, with the help of one or two pupils, has demonstrated. 



