1906J Nature Study No. 36. 91 



be found upon trial that this charcoal residue, although it will 

 not burn with a flame like the gas, will slowly burn away with a 

 glow when held by a wire in the flame of the lamp. 



It seems from this experiment that when wood is heated in 

 a closed space, it breaks up into other substances besides charcoal 

 and water. This will explain too in part, the manufacture of 

 charcoal and wcod alcohol by the destructive distillation of 

 wood, that is by heating wood in closed vessels, and the pro- 

 duction of coke (carbon) and coal gas from bituminous coal by 

 destructive distillation. 



Let the children char small samples of starch and sugar try 

 whether they contain water and whether combustible gases 

 are formed when they are decomposed by heat. The last ex- 

 periment may be performed hv hpatinn- o i:<-i-i~ -* > 



ERRATUM. 



On page 90, line 26, for "Chemical or physical mixture" read 

 'Mechanical or physical mixture." 



,w--.WV^.J \JL 



similar composition, are called carbohydrates. The fitness of 

 this name should be shown from its derivation. 



In all this work, the teacher is supposed to act only as the 

 director cf experiments and as the referee in deciding the validity 

 of the arguments and inferences. His skill is measured by the 

 success he has had in inducing each pupil to do his own observing 

 and thinking independently. 



After a careful review of the whole ground, the children 

 should retain a good working idea of chemical union will see 

 that heat tends to separate substances that have been chemically 

 united will understand what agricultural lecturers mean by car- 

 bohydrates will know that when carbohydrates are heated in 

 a closed place until they decompose they break up into carbon, 

 water, and other substances liquid and gaseous will see that 



