460 



SCIENCE. 



[Vol. IV., No. 93. 



cipally galena, anglesite, niimetite, and wulfenite, 

 with very little quartz and caleite, the gangue being 

 for the most part hydrated oxide of iron. It also 

 carries gold and silver, and zinc is present probably 

 as a silicate. Below the water-level it is composed 

 chiefly of pyrite, arsenopyrite, galena, blende, and a 

 few other sulphides, besides silver and gold. 



The ore-deposits are confined to a mass of crushed 

 limestone between the main fault and the quartzite. 

 Those of any size are always capped by caves, or in 

 some way connected with them and with fissures. 

 The caves were probably formed subsequent to the 

 deposition of the ore, being due, partly to the action 

 of water carrying carbonic acid, and partly to shrink- 

 age of the ore from decomposition. Since the latter 

 occurred, the ore has in many instances been redis- 

 tributed by the flow of underground waters, whose 

 former presence is indicated by stratification of por- 

 tions of the ore-bodies, and by traces of aqueous 

 agencies in the surrounding limestone. 



The constituents of the ore were probably derived 

 by solution from some massive rock, not sedimentary, 

 as assays of the country rock show that they could 

 not have been so derived. The solutions were due 

 to solfataric action, incident to the eruption of large 

 masses of rhyolite. They entered the limestone from 

 below, through fissures ; and the greater part, at least, 

 of the ore, was deposited by direct substitution for 

 that rock. The limestone was fissured and crushed 

 in many directions by the various faulting move- 

 ments, and gave free ingress to the ore-bearing solu- 

 tions, which naturally followed the channels of least 

 resistance, and deposited the ore in masses of very 

 irregular form. These are well shown in the model. 



From the year 1869 up to the present time (1884) 

 the Eureka district has produced about sixty million 

 dollars of gold and silver, and about two hundred and 

 twenty-five thousand tons of lead; and, as already 

 stated, the largest portion of these metals was derived 

 from the Ruby-hill mines. 



TWO LARGE SUN-SPOTS. 1 



The figures of sun-spots given with this article are 

 from drawings made at the observatory at Palermo, 

 and represent two of the largest spots observed dur- 

 ing the last two years, so remarkable for the number 

 of spots seen. Not only was their extent (which is 

 readily appreciated by comparison with the figure of 

 the earth given on each plate) immense, but the 

 changes which were seen to take place were most 

 rapid. 



The first appeared on the eastern limb of the sun 

 on June 25, 1883, about at latitude +7° 55'. After 

 undergoing various transformations, it offered, on 

 the 30th of June, the curious aspect shown in fig. 1. 

 The spot was double; and its extreme length from 

 east to west was not less than ten earth diameters, or 

 about 3'. Considerable movements were agitating it. 

 Two days afterward, on the 2d of July, the two parts 



1 Reproduced, with the cuts, from%L' Astronomie. 



had separated, and between them the photosphere 

 shone with marked whiteness. From day to day 

 this separation increased, until the 8th, when the spots 

 disappeared on the western limb, after a deviation 

 toward the north of 2° 30/. From the 28th of June 

 to the 2d of July, long, brilliant tongues, ending in 



Earth 



A h^'^0-- 







:Mim : Mi 



^| 



: \;nX*'W^ : '- '' -tit-fir ■ ■: 



-~ytM 







■ " - "' : . ^ * r 



- ; l 





-•■•; - 7 



Fig. 1. 



red hydrogen flames, were seen extending into the 

 umbra; and a yellow coloring was observed on the 

 penumbra and on some of the tongues, perhaps due 

 to the presence of sodium (fig. 2). 



This large spot was preceded and followed, on the 

 limbs of the sun, by small but brilliant solar protu- 

 berances. It returned July 2, at latitude 8° 11', much 

 smaller and more regularly shaped, to make once more 

 the tour across the disk of the sun, and disappeared 

 at latitude +8° 23', not to be seen again. 



The second spot (figs. 3 anil 4) was first seen on the 



Earth 





Fig. 2. 



eastern limb, on the 10th of July, in latitude —7° 40'. 

 It offered a strange appearance, and appeared to be 

 the seat of much disturbance. On the 25th the 

 centre was covered with luminous points which were 

 in constant motion; and some strange lines of light 

 seemed to be suspended over the umbra.- The diam- 



