556 INDEX. 



Page. 



Scientific society, a proper method of organizing 468, 511 



Secondary discharge observed between parts of a cloud 393 



Self- repulsion of galvanic electricity less than of mechanical elec- 

 tricity ^36' ^42 



Shakspeare, meteorological quotation from 452 



" Sheet-lightning," explanation of 365 



Ships, the lightning-rods of, safer when not passing through the 



Silliman, Prof. B, observation by, of the effects of lightning strokes. 377 



Small, Mr. Alexander, observation by, of a lightning stroke 388 



Smallwood, Dr., observations by, on atmospheric dust and smoke. 256 



Smallwood, Dr., observations by, on ozone referred to 168 



Smithsonian lecture-room, characteristic features of 420 



Smithsonian meteorological observations established in 1849 26 



Smithsonian tower, observation at, of peculiar effects of lightning. 391 



Smithsonian weather-map plotted from telegraphic despatches_290, 439, 440 

 Smoke and microscopic matter carried by the wind to great distances 255 



Smyth, Prof. Piazzi, observation by, of atmospheric dust on the 



peak of Teneriffe 166 



Snell, Prof. E. S., meteorological observations by, at Amherst 178 



Snow, a protector of the ground from low temperatures 210, 211 



Snow fall, directions for measuring 3 



Social laws, the uniformity of, revealed by statistics 6 



Soils, different capacity of, for retaining heat 194 



Solar energy expended and stored in plant growth 9 



Solar radiation, researches of Pouillet on 149, 150 



Solar radiation the source of vegetable and animal power. 122, 126, 137, 458 



Sound, absorption of, by various substances 414, 415 



Sound intermittently heard off the coast of Maine 520 



Sound, reflection of, observed at short distances 417 



Sound refracted by the action of wind 522 



Sound, refraction of, not observable at short distances 418, 419 



Spark, electric, exhibiting a transfer of matter from conductor 336 



Spark, electric, observed only at interruptions of conductor 339 



Speculation too often indefinite and loosely framed 311 



Speculative tendency preferable to a too positive tendency 311 



Sperm-oil employed for light-house illumination 477 



Statistics the discoverer of moral and social laws 6 



Steam, electricity from, explained by Faraday 347 



Steam-engine a less efficient machine than the human body 127, 458 



Stellar heat regarded as the temperature of space 147 



Sterility of the Rocky-mountain region 68, 70 



Storms, eastward progress of, in North America 294 



Storms from the northeast, theory of 305 



Storms not necessarily rotatory 306 



Storms, the development and progress of, indicated by isobars 29 



