APPENDIX II 69 



vegetable kingdom. His experiments are published in 

 his works, and are well worth reading. 



Experiment 32. If an explosion is to be avoided 

 great care must be taken to follow exactly the directions 

 in the text. The beginner had better adopt the method 

 described in the Note, but a teacher will find the experi- 

 ment as described in the text very effective. 



Chapter VII. Some valuable papers on the way in 

 which nitrogen is supplied to plants will be found in the 

 Journal of ike Royal Agricultural Society, vol. ii. part 

 iv. No. 8. 



II 



On the Use of the Balance 



IN several of the experiments described in the text, 

 accurate weighing is required in order to obtain a satis- 

 factory result. In some cases the quantity to be weighed 

 is very small, as for instance the ash left on burning 

 leaves. It is indispensable, therefore, that an accurate 

 balance and a good set of weights be obtained. It is 

 almost impossible to weigh accurately unless the balance is 

 enclosed in a glass case. The French weights (grammes) 

 will be found the most convenient, as they are divided 

 into tenths, and consequently can be easily added and 

 subtracted. 



Before trying any experiments in which weighing is 

 required the student should practise weighing, so as to 

 learn how to obtain an accurate result. On examining 

 the balance he will notice a little brass stud in front. 

 On turning this, tne beam of the balance is raised off 

 the brass pegs that support it, and is able to swing 

 freely. 



