372 



THE POPULAR SCIENCE MONTHLY. 



have been well prepared, and which ap- 

 proach more or less to the level of his own ; 

 but to teach a class of little boys, to realize 

 their difficulties and to appreciate their igno- 

 rance, to understand the perplexity which 

 oppresses them in the presence of state- 

 ments long since axiomatic to ourselves, re- 

 quire a mature and versatile intelligence, a 

 mind which can communicate childish knowl- 

 edge as readily and as joyously as it solves 

 recondite problems ; a combination of rare 

 gifts with long and conscientious training. 



And thus it is that the zeal for scien- 

 tific teaching and the gathered scietnific ex- 

 I perience of the last fifteen years have only 

 issued now in the books which form the 

 subject of our notice. Scientific class-books 

 hitherto have been either too difficult or too 

 easy. They have been unavailable for be- 

 ginners without the intervention of a prac- 

 tical teacher ; or, in their effort to be popu- 

 lar and simple, they have abdicated half their 

 value as instruments of educational disci- 

 pline. In these books both extremes are 

 avoided. Every stage of their teaching is 

 based upon experiment ; no law is enunci- 

 ated till it has been proved. From first to 

 last the student finds himself in immediate 

 contact with Nature. His empirical knowl- 

 edge of external things is systematized ; 

 simple every-day phenomena reveal to him 

 their principles and rationale ; he walks 

 forth with a new eye to discern the mean- 

 ing and the beauty of familiar sights and 

 sounds, and with a mind upon the stretch for 

 fresh discoveries. And, on the other hand, 

 no previous training is essential to the 

 teacher who adopts them as his guide. Any 

 man, ignorant even of the first principles of 

 chemistry and physics, yet fairly dexterous 

 and intelligent, who will patiently master 

 the books, and try each experiment for 

 himself, is in a position to transmit their 

 contents successfully and clearly. The of- 

 ficer may lecture to the soldiers of his regi- 

 ment, the clergyman to the artisans of his 

 parish, the national school-master to the 

 children of his school. Managers of schools, 

 deterred as yet from including science in 

 their course through lack of teachers and 

 of text-books, will find their difficulty re- 

 moved. . . .We tender them our hearty thanks 

 for work which marks a stage in the advance 

 of scientific education. Its lingering prog- 



ress hitherto has been owing to. the want, 

 not of zealous champions, but of united 

 action. The labors of its advocates are now 

 beginning to converge. The leaders of sci- 

 ence and the leaders of education are draw- 

 ing close together on the one side eager 

 to hnpart, on the other ready to receive, ad 

 vice and guidance. By the publication of 

 these books the most serious of the obsta- 

 cles which have kept them separate is re- 

 moved. 



MISCELLANY. 



Length of Guns. General Morin, in a 

 discourse delivered before the Paris Acade- 

 my of Science, noted this curious circum- 

 stance, that, though different kinds of pow- 

 der may give equal speed to a projectile, 

 they may differ very much from one another 

 in the pressure they exert upon the walls 

 of the cannon. He further remarked that 

 all the grades of powder that have been 

 tested undergo entire combustion, and con- 

 sequently produce all their effect in pieces 

 whose length is 12 times their calibre. But 

 yet the greater part of the field-pieces in 

 use have a length equal to 30 times their 

 calibre. They might be cut down, therefore, 

 without prejudice to their efficiency, and 

 thus their portability would be increased. 



Late Researches on the Gastric Jnice. 



The gastric juice of the human stomach 

 has lately been made a subject of special 

 study by Dr. Leube, of Erlangen, who gives 

 the fruits of his work in an elaborate paper 

 read at the recent Rostock Congress. He 

 obtained the juice for his experiments by 

 means of a tube introduced into the gullet. 

 The gastric juice obtained from the stom- 

 ach, empty and cleansed by an injection of 

 water, is slightly acid, doubtless owing to 

 the irritation caused by the injection and 

 the contact of the instrument. Its diges- 

 tive power is weak. In the course of his 

 experiments with this fluid, Leube found 

 that cheese is digested more rapidly than 

 the albumen of a boiled egg, and the latter 

 more rapidly than the albumen of a raw 



pcrcr 



c oo- 



Experiments made with quassia demon- 

 strate that this substance does not exert 

 any special exciting action upon the seore- 



