NOTES. 



575 



with the earth, could not have any material 

 influence in attracting the lightning from 

 the clouds ; if it had, then the houses with 

 tin roofs, many of them without lightning- 

 rods, now so common, would be in great 

 danger, whereas they are not struck often- 

 er than houses with tile roofs. The pres- 

 ence of iron, however, might increase the 

 danger of fire after the house had been 

 struck ; for, if we place a combustible sub- 

 stance between two conducting surfaces, it 

 is generally sure to take fire when an elec- 

 tric current is passed through it from one 

 of the conducting surfaces to the other. So, 

 if lightning should strike a house, it would 

 find its way to any masses of metal within 

 the building and ignite whatever combusti- 

 ble matters it passed. In view of this fact, 

 and of the present very extensive use of 

 metal in house-construction, the provision 

 of suitable conductors to divert electrical 

 currents from the combustible parts of the 

 building has become more important than 

 ever. 



Was it Volcanic or Cosmic Dust ? Mr. 



W. Mattieu Williams is of the opinion that 

 the long continuance of the glowing twi- 

 lights tells against the validity of the vol- 

 canic-dust theory ; for that dust must have 

 settled by this time, or, if so much of it has 

 continued to float in the atmosphere, it 

 should have shown its presence more pal- 

 pably than it has done. The two alterna- 

 tive hypotheses to this one, worthy of seri- 

 ous consideration, are : 1. That the earth, 

 and possibly the whole or a large portion 

 of the solar system, has, in the course of 

 its journey through space, passed through a 

 region unusually rich in meteoric dust ; or, 

 2. That an unusually large amount of aque- 

 ous vapor has been raised to the upper re- 

 gions of our atmosphere by increased solar 

 activity. Apparently in favor of the mete- 

 oric theory is the statement of F. Mangini, 

 that on three days in February and March, 

 1885, when the glows, accompanied by rain, 

 were especially remarkable, he collected at 

 Reggio, in Calabria, some new-fallen red 

 dust, which, when examined under the micro- 

 scope, seemed to consist of mica, quartz, 

 and irregular polyhedric crystals. Analysis 

 brought out magnetic iron oxide, sulphuric 

 and phosphoric acids, silica, calcium, mag- 



nesium, aluminum, nickel, and arscnious, 

 ferric, and manganous oxides. The dust 

 did not come from Etna, because the wind 

 was blowing in the opposite direction, and 

 Etna dusts are black ; nor from the Sahara, 

 because Sahara dusts contain no iron. 



Oranges in Palestine. The climate and 

 soil of Palestine are well adapted to the cul- 

 tivation of the orange, which, according to 

 Consul Merrill, there suffers from no diseases 

 or parasites of any kind. The trees appear 

 to flourish best near the sea, and the orange- 

 groves are for the most part near Jaffa and 

 Gaza. In Jaffa there are five hundred gar- 

 dens, of which one hundred and fifty are 

 ranked as first class, all the gardens together 

 containing about 800,000 trees. The trees 

 are set about fifteen feet apart, while the 

 ground between them is planted with small 

 fruits or vegetables. The sweet lemon is 

 used as the stock, and the variety of orange 

 desired is grafted upon it. The trees are 

 watered every week in the summer, at a cost 

 per season of about one fifth the value of 

 the crop in gardens of the first class. The 

 Jaffa oranges proper, the only kind export- 

 ed, are oval, or lemon-shaped. 



NOTES. 



M. Domeyko has summarized the results 

 of forty-six years of observations on earth- 

 quakes in Chili. They are more frequent 

 in the northern part of the country, where 

 there are no volcanoes, and the Andes are 

 fifteen thousand feet high, than in the 

 southern part, where there are volcanoes, 

 and the mountains are only a third as high. 

 The effects of the shocks on buildings de- 

 pend more on the nature of the soil than on 

 the violence of the spasms. The sea-phe- 

 nomena are of two kinds : local, or oscillat- 

 ing, when the waters retire to beyond the 

 lowest-water mark, to return in waves a hun- 

 dred feet high beating upon the coast and 

 destroying everything they reach ; or, when 

 the shocks occur at a distance, the water 

 runs along the coast in a grand wave with- 

 out previously retiring. In the more severe 

 earthquakes, when there are several shocks 

 in the same day, it is generally the second 

 or third one that produces the greatest 

 destruction. The destructive effects of an 

 earthquake are never as considerable in the 

 interior of a mine as at the surface. 



M. Qukntin Paul Desains, of the Physi- 

 cal Section of the French Academy of Sci- 

 ences, died after a very short illness, about 



