INDEX. 553 



Oersted's discovery of the effect of galvanism on magnetic needle, 



illustrated 427 



Oil barometer proposed, but not satisfactory 421 



Oil, colza, employed for light-house illumination 477 



Oil, lard, experiments on, for light-house illumination 479 



Oil, mineral, employed for light-house illumination 476, 499 



Oil, sperm, employed for light-house illumination 477 



Oils, the relative fluidity of, method of comparing 480, 505 



Olmsted, Prof. D., investigation of tornadoes by ,_ 292 



Olmsted, Prof. D., observation by, on electrical effects from interrup- 

 tion of conductor 840 



Organic bodies raised to a state of " power," as instable compounds 117 



Organic compounds chemically more complex than mineral 115, IIG 



Organic matter principally gaseous 8 



Organic molecules compounded under the direction of the vital 



principle 116 



Organization so far as observed derived from vitality, not the con- 

 verse 459 



Ozone an allotropic condition of oxygen, produced by lightning 344 



Ozone, various effects of, noticed 168 



Paint not injurious to the conducting power of lightning-rods Q43 



Palmieri, apparatus by, for drawing electricity from the air 053 



Panoptic curve for floor and seats of lecture-rooms 420 



Patented lightning-rods of little value 387, 402 



Peltier, hypothesis by, as to atmospheric electricity 348 



Peltier, observations by, on different electrical conditions of clouds. 363, 364 



Pennsylvania, attention given to meteorology by the State 448 



Periodicity sometimes observed in storms 304, 305 



Petroleum inferior to lard-oil in illuminating power 509, 510 



Petroleum lamps, the danger of explosion from 500 



Petroleum substituted for lard-oil in light-houses, only because 



cheaper "1" 



Petroleum, surface attraction of, very great 508 



Petroleum, test of inflammability of, by flashing 502 



Photometers employed in testing illuminating oils 484, 485,488 



Physical geography, a modifier of climate 63 



Phj'sical observatory, importance of 461 



Physical observatory, the method of establishing 464 



Piddington, theory of hurricanes by 306 



Plants and animals composed chiefly of solidified gas 8 



Plants built up by the absorption or conversion of solar radiations. 122 



Plants, germination of, effected by the energy stored in the seed or 



tuber 121, 124 



Plants the recipients and distributors of solar energy 9 



Plants, the solid substance of, derived almost entirely from the air. 122 



