86 SUPPORTERS OF COMBUSTION OXYGEN 



of lead bears to the metal lead, being the same thing with 

 respect to that metal, is usually employed for the purpose 

 of obtaining this gas for experiment, on account of the quan- 

 tity of oxygen which it contains, and the readiness with which 

 it gives it off; specimens of oxide of manganese being ex- 

 hibited. As the mode of obtaining oxygen by igniting the 

 peroxide of manganese was inconvenient to exhibit, that by 

 sulphuric acid and heat, using a glass retort, was preferred, 

 for experimental demonstration ; and the influence of oxygen 

 as a supporter of combustion was exhibited, in its effect on 

 a lighted match, a lighted taper, and inflamed phosphorus, 

 compared with that of the air on the same combustibles. 



The subject of Pneumatic Chemistry having thus been 

 opened, the method of collecting and preserving gases by 

 means of the hydro-pneumatic apparatus, or pneumatic trough, 

 was explained ; for the sake of familiar illustration a portion 

 of air being blown into a transfer-jar standing over water on 

 the shelf of the trough, by means of a pair of bellows, and then 

 transferred to a bladder, and directed on the flame of a lamp 

 by means of a blowpipe. The history of the discovery and 

 the properties of OXYGEN GAS were then entered upon ; those 

 properties which could be numerically stated, as its specific 

 gravity, compared both with hydrogen gas, as the lightest sub- 

 stance in nature, and with common air, being shown in a 

 diagram. The effects of oxygen as a supporter of combus- 

 tion, were then further exemplified, in the combustion of sul- 

 phur and iron, and the results examined ; lastly, were men- 

 tioned the functions of oxygen in respiration *. 



* The fact that a small animal, confined in oxygen gas, lives about three 

 times as long as when confined in the same bulk of atmospheric air, was of 

 course here stated ; but that experiment was purposely omitted ; as the 

 Teacher was unwilling to familiarize his pupils with the pain to which 

 the animal must necessarily have been subjected. For the same reason he has 

 refrained, throughout his instructions, from making the slightest expe- 

 riment on living animals, and from all in which even the appearance of suf- 

 fering might have been produced, or in which it might have been supposed 

 that the animal, though dead when made the subject of the experiment, 

 might have previously suffered pain, in being prepared for it. Cruelty to 

 animals, in all its degrees, is strictly prohibited by the Laws of the Schools ; 

 and the Teacher's own view of the subject is this: that when the reasoning 

 faculties have attained their mature and cultivated activity, his pupils will 

 be able to judge, to what extent the performance of experiments involving 

 the suffering, or the death, of animals, may justifiably be carried ; but until 

 that state has been attained, no degree of knowledge derivable from such 

 experiments, would compensate for the production in their minds of the 

 basis for inhumanity, which might be formed, by their being accustomed to 

 witness, with complacency, or with indifference, either the actual, or the 

 apparent suffering, of the animals employed. 



The Moral Philosophy of the wholesome popular impressions respecting 



