SCIENCE IN SECONDARY SCHOOLS. 201 
NATURE or WATER. 
You believe that you have obtained this clue to the composition of water— 
that it consists of the gas which is called water-stuff, or hydrogen (because it 
affords water when burnt) and oxygen: as you know that all other things 
which you have burnt combined with the oxygen. But nothing must be taken 
for granted in our work: it is possible that the oxygen in air is not alone 
concerned ; cannot you devise some method of using oxygen in a form in which 
there can be no doubt that if water is obtained it is formed from oxygen and 
hydrogen alone? How did you burn carbon with oxygen alone? 
You are now satisfied that you have established the fact that water con- 
sists of hydrogen and oxygen. Is it not worth while to submit the oxides 
generally to the action of hydrogen? Will you not be able to test lime if 
you find that they all give up their oxygen to hydrogen? The results enable 
you to classify the metallic oxides in two groups; although you have not yet 
solved the problem regarding lime, have you not narrowed it—is it not clear 
that if it be a metallic oxide it is the oxide of a metal of a particular kind? 
Perhaps by studying the action of spirit of salt, which dissolves oxides, it 
may be possible to obtain further information of assistance in solving the 
problem as to the nature of lime. Where does the hydrogen come from which is 
obtained when zine is dissolved in muriatic acid? As this is a solution of 
spirit of salt in water, obviously it might come from the water in the solution, 
since this is known to contain hydrogen; it might come, however, from the 
dissolved gas. How shall we decide whether or no this be the case? We 
must eliminate the water, must we not? Try the experiment without water. 
There are still two ways possible in which the gas may be formed—it may 
be present either in the metal or in the gas. Can any argument be adduced 
in favour of the one view or the other? Zinc oxide is produced on a large 
scale for making white paint (zinc white paint) and it should be possible 
to ascertain if water be formed on burning the zinc; if not, the experiment 
must be tried. 
As there is reason to suppose that the hydrogen is contained in the spirit 
of salt, it is probable that the zinc displaces it, combining with whatever is 
associated with the hydrogen. How does the oxide behave towards the acid— 
like lime? It dissolves quietly. What then becomes of the hydrogen, sup- 
posing this to be in the spirit of salt—is not its disappearance to be accounted 
for, if it combine with the oxygen in the oxide? The product in solution will 
be the same, will it not, according to this view, whether zinc or zinc oxide 
be dissolved : in what will the difference consist? Is water formed when zinc 
oxide is acted upon by the spirit of salt? Experiment shows that a liquid 
is formed—can this be water? As the water will be in presence of the gas, 
it will be saturated with it—the gas must be got rid of from the liquid to 
obtain proof that water is formed. 
Having ascertained that water is formed when zinc oxide is acted upon 
by spirit of salt, the production of water becomes a proof of the presence of 
oxygen—you are able now to test lime—again water is obtained. It is therefore 
established that lime is an oxide—probably the oxide of a metal like magnesium 
or zinc. Limestone stuff is therefore a distinct type of earthy substance, 
different from the earthy metallic oxides, formed by the association of a 
metallic oxide with a non-metallic oxide. You have yet to extend your ex- 
periments to the other metallic oxides to ascertain whether they all form 
compounds similar to limestone stuff. 
If a course of experiments with the metals and metallic oxides (iron, copper, 
zinc, lead, magnesium, etc.) and acids (muriatic, nitric, sulphuric) were introduced 
here, there would be considerable opportunity of cultivating preparative skill. 
LireraRny Work. 
In carrying out such a course attention must ever be paid to the literary 
side of the work. Rough but clear notes, of the arguments used, of the things 
done and of the observations made, must be jotted down, from time to time, 
