OcToiiKi: !i, 1903.] 



SCIENCE. 



4<)7 



■■ IJiil tliey are not lenl folk*, you know . I wish 

 they were.", 



" Well," said her uncle, " that gas is nothing 

 more nor less than a collection of real fairies 

 \ritli green dresses on." 



Jessie opened her eyes very wide toward the 

 j,'rcen jar. * ' * 



" Do they liave real legs and arms?" asked she, 

 looking curiously at the green gas. 



"They certainly liave arms— or rather an arm, 

 for this kind has only one. And I suppose they 

 liave legs, for they run around briskly enough 

 -omctimes.'" 



"What are their names?" asked Jessie. 



" There are so many of them, and they are so 

 small and so much alike, that no mortal has ever 

 been able to get acquainted with them separately. 

 But the wise men who first found out about them, 

 named the whole tribe Chlorine, from the color 

 of the dresses which they wear. Chlorine is 

 taken from a Greek word which means grocn. 

 But this is only one tribe. There arc sixty or 

 seventy others — all different, and all having dif- 

 ferent names." 



"Do they all dress alike?" asked Jessie. 



" Each tribe has its own uniform, which is 

 usually the same, but you can find almost every 

 color among different tribes. One tribe — a first 

 cousin to Chlorine — always wears a dark red 

 dress, and there are several that have a wonder- 

 ful magic cloak that makes them quite invisible." 



^Vllile this may not be the deepest kiud 

 of scientific literature, we must allow that 

 if our children are to listen to fairy stories 

 these are good ones. 



It i.s interesting to note at this point 

 that the conversational style adopted in 

 this book was used very satisfactorily one 

 hundred years ago for books written for 

 children of larger growth. In 1806 Jane 

 Marcet published a book entitled 'Conver- 

 sations on Chemistry. ' A note beneath the 

 catalogue title of this book in H. Carring- 

 ton Bolton's 'Bibliography of Chemistry' 

 reads: 'This work passed through more 

 than twenty editions, having a success now 

 difficult to comprehend.' The writer, the 

 preface tells us, is an admirer of Sir 

 Humphry Davy, and has attended his 

 lectures at the Roval Institution. The 



conversation is supposed to take place be- 

 tween a Mrs. B.. who is a teacher, and two 

 young ladies. The following selection is 

 characteristic. 



Emily. " And how do you obtain the oxy- 

 muriatic acid? " 



Mrs. B. "In various ways; but it may be 

 most conveniently obtained by distilling liquid 

 muriatic acid over oxyd of mangane.se, whicli 

 supplies the acid with the additional o.vygen. 

 One part of the acid being put into a retort, with 

 two parts of the oxyd of manganese, and the heat 

 of a lamp applied, the gas is soon disengaged, 

 and may be received over water, as it is but 

 sparingly absorbed by it. I have collected some 

 in this jar." 



Caroline. " It is not invisible like the gen- 

 erality of gases; for it is of a yellowish color." 



Mrs. B. " The muriatic acid extinguishes 

 Uame, whilst, on the contrary, the oxy-muriatic 

 makes the flame larger, and gives it a dark red 

 color. Can you account for this difference in the 

 two acids ? " 



Emily. "Yes, I think so; the muriatic acid 

 will not supply the flame with the oxygen neces- 

 sary for its support; but when this acid is further 

 oxygenated, it will part with its additional 

 quantity of oxygen and in this way support com- 

 bustion." 



Mrs. B. "This is exactly the case; indeed the 

 oxygen added to the muriatic acid adheres so 

 sliglitly to it that it is separated by mere ex- 

 posure to the sun's rays. This acid is decomposed 

 also by combustible bodies many of which it burns, 

 and actually inflames, without any previous in- 

 crease of temperature." 



Caroline. " That is extraordinary indeed. I 

 liope you mean to indulge us with some of these 

 experiments? " 



Mrs. B. " I have prepared several glass jars 

 of o.xy-muriatic acid gas for that purpose. In 

 the first we shall introduce some Dutch gold leaf. 

 — Do you observe that it takes fire ? " 



The interest aroused in the subject by 

 tliis little book can be explained, it seems 

 to me, by the nature of the description. 

 There is a vividness to it that a bald state- 

 ment of fact lacks. The personal element 

 is strong and the minds of at least three 

 persons all considering the same question 

 are reflected in the pages of the book. 



