1826»] of the British Si/stem of Chemical Instruction, 377 



road-maker; and tin is particularly applied by mechanics to 

 designate that useful household ware the principal ingredient ot 

 which is iron. Our scientific verbs, in many instances, convey 

 no distinct notions to their understanding ; and a lecturer who 

 uses them without explanation, might as well speak in a foreign 

 language. He says " the metal is oxidized," where they would 

 only understand the term rusted. He describes an acid as 

 saturated by an alkali, iron as oxidized in the smith's fire, and lime 

 as neutralized by carbonic acid gas ; whereas many of his class are 

 perhaps only accustomed to hear, " the acid is killed," " the 

 iron is poisoned," " the hrae is dead." 



If the conversational system be adopted, all such misunder- 

 standings will quickly be removed, and a sensible lecturer will 

 gladly avail himself of it, as the best means to discover his own 

 defects in teaching. If the impartial questions and lively sug- 

 gestions of pupils were freely permitted and generally encou- 

 raged, various important discoveries would naturally ensue, and 

 many of the systematic errors and absurdities which have hither- 

 to disgraced all sciences, would have been quickly discovered 

 and banished, or perhaps never adoped. 



In laying a sound foundation for scientific acquirement in the 

 youthful mind, it is very unwise to encourage (by example or 

 commendation) a taste for hypotheses and speculations. With 

 such an imaginative habit in early life, nothing is easier than to 

 be mistaken. The rage for systematizing is perhaps the greatest 

 bar to the attainment of truth in every branch of knowledge: 

 in the science of chemistry it has been actively mischievous. 

 In the last century. Phlogiston, like a pagan deity, occupied all 

 minds to the exclusion of every important truth which interfered 

 with its ideal existence. Since its downfall, oxygen was main- 

 tained to be the sole acidifying principle, and the attraction of 

 the mass upheld as destructive of definite proportions, as strenu- 

 ously as if their champions could not err. A brief essay of this 

 nature would not have space to enumerate all the chemical 

 hypotheses that were downright errors : the words are now 

 looked on as nearly synonymous. In the interesting sciences 

 of geology, electricity, and meteorology also, this unfortunate 

 taste for generalizing favourite facts has hitherto been very pre- 

 valent, and in consequence, the authors have been universally sus- 

 pected ; insomuch that an experienced reader learns to distrust 

 their opinions and inferences as completely as if they proceeded 

 from professional advocates on a point of law. A novice h\ 

 science, however, too often acquires corresponding bad habits 

 of speculating and taking things for granted, and frequently 

 loses valuable time in the study of authors who dogmatize on 

 the laws and operations of nature, as confidently as if they were 

 in her secrets. 



Young students are frequently deceived by this plausible 



