142 



THE POPULAR SCIENCE MONTHLY. 



of tea, and is essentially the same principle 

 that gives value to those substances and to 

 the mate of Paraguay and the coca of Peru. 

 Thus, in the several drinks prepared from 

 these substances, the Chinese, the Arabs, 

 and the Indians of Mexico and South Amer- 

 ica enjoy the influence of the same cheering 

 but not inebriating agent. Cacao and choco- 

 late differ from the other beverages named 

 in that they contain a notable proportion of 

 nutritious elements which exist in the oth- 

 ers only in minute quantities. 



The Qnestion of Short-Sightedness in 

 French Schools. — A commission appointed 

 by the French Government to investigate the 

 question of short-sightedness in schools re- 

 cently made a report through Dr. Gariel. It 

 declares that the affection is caused by the 

 efforts of the pupil to accommodate his vis- 

 ion to the requirements of the position in 

 which he iiuds himself, and by his bending 

 over. These effects are provoked by defect- 

 ive lighting, badly fitting seats and desks, bad 

 methods of writing, premature instruction, 

 and too fine print. The commission recom- 

 mend, for books, yellowish - tinted paper; 

 that each line with its white should occupy 

 a minimum vertical space of 3-384 millime- 

 tres; and that there should not be more 

 than seven letters to each current centime- 

 tre of text. Furthermore, every book should 

 be rejected which is not readable to good 

 eyes eighty centimetres or thirty-one inches 

 off in the fight of a standard candle one me- 

 tre away, and every map that is not distinct 

 under the same conditions at a distance of 

 forty centimetres, or sixteen inches. In re- 

 gard to habit in writing the committee exacts 

 George Sand's condition of " straight writing, 

 on straight paper, with a straight body." In- 

 struction should not begin too early, at least 

 not in writing on paper ; and the child should 

 not be put at it till it has learned to trace 

 the letters on a board, upright, and without 

 linking them together. In the matter of 

 seats and desks, the committee appear to 

 exact that the horizontal distance between 

 the edge of the desk and the front of the 

 seat one or two places back shall be rigor- 

 ously negative ; then the child will not be 

 able to bring his chin do^-n to his desk. 

 The back should be inclined to fit the pupil's 

 back and give a position of rest, and the 



desks should slant so that the paper lying 

 on them should be perpendicular to the 

 visual rays. The larger classes should have 

 movable chairs. If there is not enough 

 light, the pupils should be allowed to hold 

 their books so that they can get the most of 

 it. An Italian journal has published a mod- 

 el of a seat well adapted to fit the back of 

 various sizes to suit deficient eyes, and so 

 adjusted that the child can take a nap, if 

 sleepy, without suffering. The hardest ques- 

 tion the committee had to meet was that 

 regarding the admission of light. It was 

 agreed that a sufficient illumination of the 

 darkest part of the room should be the stand- 

 ard, and that a bit of sky not less than thir- 

 ty centimetres, or twelve inches, in vertical 

 diameter ought to be visible from the least 

 favored spot; but the expediency of bilateral 

 illumination does not yet seem to be deter- 

 mined to thesatisf action of all: some thought 

 cross-lights might give trouble ; others sug- 

 gested that this could be avoided by making 

 the lijrht from one side much stron2;er than 

 from the other, or by making the light come 

 from above or from behind. 



Natural Gas as a Sonrce of Fnel. — An 



important change in the conditions of manu- 

 facturing in Pittsburg is promised by the 

 introduction of natural gas as fuel in place 

 of coal. The gas, which is principally car- 

 bureted hydrogen, or the fire-damp of the 

 mines, is obtained abundantly in the neigh- 

 borhood of the city, and even within its 

 corporate limits, by boring wells. Much of 

 it has been met in the past in boring for 

 petroleum, and when found under such cir- 

 cumstances it was regarded as a nuisance. 

 Some of the wells thus discovered have 

 already been applied to economical uses, 

 and found as valuable as if they had been 

 petroleum-wells. Such wells are employed 

 for burning brick at New Cumberland, and 

 in the manufacture of pottery at East Liv- 

 erpool, of cutlery at Beaver Falls, and of 

 glass-ware at Rochester. The gas of six 

 wells is brought through pipes twenty miles 

 to the city and used to heat the boilers of 

 an iron-manufactoiy ; and it has been found 

 that, where the distance of the supply is so 

 short that the gas can be brought in with- 

 out its pressure being wholly lost in piping, 

 it can be made a valuable addition to the 



