302 REPORT—1890. 
ditions, the origin of rain, the differences between waters from various 
sources, and the method of separating water from the associated foreign 
matters will have been brought home to the minds cf the pupils. 
6. As the water is heated to boiling in the flask, if attention be paid 
to all that occurs, it will probably be noticed that bubbles separate from 
the water, rising up through it and escaping at the surface ; frequently 
the bubbles adhere for a time to the flask. Let the experiment be 
repeated in such a way that the something which escapes from the water 
can be collected and measured; for example, a 2-gallon tin can having 
been filled with water, insert into the neck a rubber cork through which 
a bent delivery tube is passed, place the can over a burner, introduce the 
upturned end of the delivery tube into a basin of water, and insert a 
small jar over it. Heat to boiling. An air-like substance will gradually 
be driven off, but it will be noticed that after the water has been boiling 
for some time it ceases to give off gas; let the amount of gas collected 
be measured, and have the experiment repeated several times. As 
the gas does not continue to come off on boiling the water, it would 
seem that it is not a part of the water—there is so little of it, but merely 
something dissolved in the water; it is like air, and the water had been 
in contact with air—may it not be air? Let the boiled water be poured 
out into a galvanised iron pan, and after it has been exposed to the air 
for several hours let it be again boiled. The water which previously 
no longer gave off gas will now yield probably as much as before. It 
will thus be discovered that water dissolves air as well as the solid 
matters with which it comes in contact, and the presence of air in water 
will be recognised. This knowledge will be of value later on when the 
existence of animals and plants under water comes to be considered. 
7. Attention having thus been directed to the solvent action of water, let 
special experiments be made on its solvent action, using salt, sugar, suet, 
washing soda, alum, tea and coffee, field or garden soil, clay, chalk or 
limestone, gypsum, &c.; known quantities of the filtered solutions should 
be evaporated to dryness, and the residues dried (conveniently in a small 
gas cooking-oven) and weighed. Opportunity will be afforded to call 
attention to the separation of some of the substances from solution in 
definite shapes, i.e. crystals; show these under the microscope as 
well as home-made cardboard models of some of them. Let larger crys- 
tals of alum be grown, and call attention to sugar crystals. Natural 
crystals of calcite, gypsum, pyrites, quartz, fluorspar, &c. would be 
appropriately shown at this stage. The question may then be put, Does 
the water which passes through the body dissolve anything ? By evapo- 
rating urine and determining the amount of dried residue it would be 
found that a good deal of matter passes away from the body ia solution. 
8. Having directed attention to the different behaviour of different 
waters with soap, let determinations be made of the amount of alcoholic 
soap solution required to produce a lather in distilled and other waters. 
Directions for performing the soap test are easily obtained from a book 
on water analysis, and the operation is one of extreme simplicity. 
9. Other liquids should now be compared with water, such as methy- 
lated spirit, turpentine, petroleum, salad oil, vinegar, and perhaps the 
common acids—muriatic, nitric, and sulphuric—also. The noticeable 
differences between these and water—appearance, odour, taste in dilute 
solution—having been registered, their relative densities should be deter- 
mined ; also their behaviour towards water and towards each other, their 
