522 REPORTS ON THE STATE OF SCIENCE, ETC. 



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 zinc is dissolved in muriatic acid ? As this is a eolution 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 learn by inquiry 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 ol 

 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. 



Literary 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, 

 as each experiment proceeds : on no account must this be done at any other 

 time. A reasoned account of the work should then be written out at leisure, 

 in flowing language, with due regard to style, never in the inexcusable form of 

 a statement in advance of the conclusion to be arrived at ultimately, nor in 

 the graceless hackneyed form of Experiment, Observation, Inference. It should 

 never be forgotten that the prime object in view is to develop habits of 

 logical thought and logical statement, together with the habit of inquiry. 

 The clearest possible distinction must be dr.Twn, therefore, between an experi- 

 mental, reasoned inquiry into an undetermined issue and the practical demonstra- 

 tion or verification of a stated fact. It must be made clear that an experiment 

 is an act performed with the definite object either of finding out something 

 novel in the experience of the worker or of testing an assumption — that the mere 

 demonstration or verification of the truth of a statement is not an experiment. 

 The accounts should be fully illustrated by drawings and photographs. 



In order to teach the use of books and develop the habit of purposed, serious 

 reading, as wide a course as possible of reading should be associated with the 

 experimental work. The books used should be mainly of general interest, and 

 informative— books of reference, books of travel, &c. — though technical books 

 may be consulted occasionally with advantage. 



