POPULAR MISCELLANY. 



567 



ly sent from Paris to Sir William Thomson 

 at Glasgow, which was found by him to con- 

 tain electrical energy equal to something 

 over one million foot-pounds, or one-horse 

 power, for one hour. Though the battery 

 was seventy-two hours reaching him, it was 

 -found to have lost but very little of its orig- 

 inal charge, and he has since been able to 

 detect but a slight loss in a period of ten 

 days. The expectations regarding the uses 

 to which this battery can be put are doubt- 

 less exaggerated, but it seems safe to pre- 

 dict for it a large field of usefulness. It 

 can probably be employed to advantage, if 

 further experiment bears out present state- 

 ments regarding it, wherever ordinary bat- 

 teries are used, as it possesses the conven- 

 ience of these combined with the cheap- 

 ness of the dynamo-machine in the matter 

 of the currents furnished. In the electric- 

 light it will probably find an important use 

 in equalizing the currents of the machines, 

 and preventing interruption of the hght in 

 case of a temporary failure of the generat- 

 ing apparatus. It is, moreover, not impos- 

 sible that it may dispense with the need for 

 electrical distribution at all, as such batter- 

 ies placed in houses could be charged each 

 day by small dynamo-machines driven by gas- 

 engines, at but small expense and with the 

 minimum amount of trouble. 



Color-Blindness and Edncation of the 

 Color-Sense, The examinations instituted 

 by Dr. B. Joy Jeffries among the pupils in 

 the schools of Boston (including 14,469 boys 

 and young men and 13,458 girls and young 

 women) have shown that about one male 

 person in twenty-five is color-blind, while 

 the defect occurs with extreme rarity in girls 

 and women (only 0-066 per cent, of the fe- 

 male pupils in the schools). The researches 

 that have been made in Europe show that 

 a similar law as to the relative proportion 

 of color-blindness between the sexes pre- 

 vails there. The subject has been over- 

 looked until within a few years, but the 

 value of the knowledge of it that has been 

 gained can not be disputed. This knowledge 

 can be applied practically on a scale of con- 

 siderable extent in determining the vocation 

 to which boys should be trained. A person 

 who is color-blind is obviously unfit for any 

 business in which he must know how to dis- 



tinguish colors. Yet the person himself 

 and those who are around him are seldom 

 aware of his defect. If examinations are 

 regularly made in the schools and records 

 kept of them, as has been done by Pro- 

 fessor Jeffries, a sure practical test may be 

 found which can be applied directly to each 

 person, so as to guide him aright on this 

 point. The inquiries of Dr. Jeffries have 

 disclosed a great lack of knowledge of col- 

 ors, aside from color-blindness, among adults 

 as well as among the boys in the schools. 

 But very few boys of the grammar or higher 

 schools, he says, are familiar with the color- 

 names of even the primary colors, and still 

 less can they correctly apply those names 

 they do remember, when shown colored ob- 

 jects. " I have received letters from adults, 

 not color-blind, whose lack of color-names 

 had been a serious drawback to them in 

 their occupations in every-day life ; and they 

 have besought me to urge the teaching of 

 color-names and the education of the color- 

 sense in our public schools." The teaching 

 of colors and color-names has been partly 

 introduced into our primary schools, but 

 without any system ; it has been begun in 

 Europe, especially in Germany, in the lowest 

 schools, in a systematic manner. The ex- 

 emption of women from color-blindness has 

 been attributed to their familiarity with 

 colored objects and materials ; but this holds 

 only of the sex as a whole, not with refer- 

 ence to individuals, for the color-sense can 

 not be changed with practice in colors. The 

 question arises whether generations of color- 

 education have caused this sexual difference, 

 and is important ; for, if answered in the 

 affirmative, it proves that we may begin to 

 eliminate color-blindness from future gener- 

 ations of boys by teaching and exercising 

 the present generation in the perception and 

 distinction of colors. 



Climate and Health. Mr. Alexander 

 William Mitchinson has read an important 

 paper in the Society of Arts on " The Prin- 

 cipal Causes of Disease in Tropical Coun- 

 tries." It is usual to trace these causes back 

 to the climate, but Mr. Mitchinson main- 

 tains that climate has less to do directly in 

 producing disease than has generally been 

 supposed. Every climate and country has 

 its own appropriate and dietary laws, and 



