FRAGMENTS OF SCIENCE. 



573 



of being advanced in the same way ; and 

 when it is borne in mind that the force of 

 waves, the ebb and flow of tides in rivers, 

 the influence of training works in estuaries, 

 and the motion of ships at sea have been 

 subjected to experimental research, it ap- 

 pears impossible to assign a limit to the 

 range of experiments as a means of extend- 

 ing engineering knowledge. The correct 

 calculations of strains, the exact strength of 

 materials, and a strict appreciation of the 

 physical laws afi"ecting designs are of the 

 utmost importance, and the failure of many 

 bridges might be explained by a neglect of 

 these considerations. Occasionally failui-es 

 of works might be attributed to exceptional 

 causes or peculiarly unfavorable conditions, 

 but in most cases they are the result of er- 

 rors or deficiencies in design which might 

 have been avoided by a more correct appre- 

 ciation of the physical conditions involved. 



Eleetrical Effects of Spray. A corre- 

 spondent, writing to us concerning the effect 

 of various atmospheric conditions on health 

 and bodily vigor, cites his own experience in 

 a fire brigade as having led him to believe 

 that deficiency of ozone and other unfavor- 

 able conditions and the effect of atmospheric 

 impurities may be alleviated by inhalation 

 through a spray of cold water. A method 

 of ventilation of railroad cars which was 

 very comfortable to passengers riding in 

 cars so treated, but has been disused, de- 

 pended upon the application of this princi- 

 ple. Its value is further confirmed by what 

 Prince Kropotkin has said in one of his re- 

 cent articles on current science concerning 

 the theory of the development of electricity 

 by spattering water. A few years ago Herr 

 Lenard undertook a series of observations in 

 Switzerland on the electrical effect of water- 

 falls. It appeared that even small cataracts, 

 only a few feet high, send into the air con- 

 siderable charges of electricity, provided 

 they bring down a large amount of rapidly 

 dashing water. The smallest jets of water 

 that drip on the rock sides, and even roar- 

 ing streamlets, have the same effect. He 

 suggested that the chief cause of electrifica- 

 tion is the tearing asunder of the drops of 

 water as they fall on the wet surfaces at the 

 bottom of the waterfall. The experiments 

 on which these views are founded accord 



with the demonstration by Lord Kelvin and 

 Messrs. Maclean and Goto that air, even ab- 

 solutely dust free, can be electrified by a jet 

 of water. This source of electrification is 

 further shown to be by no means insignifi- 

 cant, and the amount of electricity sent into 

 the air in this way is immense. The impor- 

 tance of these facts in the economy of Na- 

 ture, says Prince Kropotkin, is self-evident. 

 " The supply of electricity in the air is con- 

 tinually renewed. The waterfalls in the val- 

 leys, the splashing of the waves on the shores 

 of lakes and rivers, and the splash of drops 

 of rain on the ground send masses of nega- 

 tive electricity into the air ; even the watering 

 of our streets and of our plants in the or- 

 chards has the same effect on a limited 

 scale. On the other side, the waves of the 

 sea, as they break against the rocks and fall 

 back in millions of di-oplets upon the beach, 

 supply the air with masses of positive elec- 

 tricity the amount of which rapidly increases 

 after each storm. And when we stand on a 

 sea beach we not only inhale pure ozonified 

 or iodized air ; we are, so to say, surrounded 

 by an electrified atmosphere, which, as al- 

 ready remarked by Humboldt and often con- 

 firmed since, must have a stimulating eilect 

 upon our nei'vous activity as well as upon 

 the circulation of sap in plants." 



The Sciences Auxiliary to Engineering. 



Among the branches of science necessary 

 for the engineer, Mr. L. F. Vernon Har- 

 court, in his address at the British Associa- 

 tion meeting, named mathematics and phys- 

 ics as of the highest importance, and as 

 those upon which the profession mainly de- 

 pends. Other sciences of considerable 

 though comparatively minor importance are 

 those of chemistry, meteorology, and geol- 

 ogy. All branches of applied mathematics 

 have to be used by engineers, or, as in the 

 case of several general principles and tidal 

 calculations, by mathematicians, for their 

 benefit; but graphic statics will probably 

 gradually supersede analytical methods for 

 the calculation of stresses, as more rapid 

 and less liable to errors, which are also 

 more easily detected in graphic diagrams 

 Pure mathematics, in its higher branches, 

 appears to have a less direct connection with 

 engineering; but applied mathematics is so 

 largely dependent upon pure mathematics 



