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THE POPULAR SCIENCE MONTHLY. 



dium burns with intense brilliancy in gaseous 

 oxygen, but in liquid oxygen would not burn 

 at all, the very low temperature ( 180) 

 hindering chemical action. Liquid oxygen 

 has an electrical resistance five or six times 

 greater than that of the gas, which itself is 

 strongly magnetic. Put under the poles of 

 an electro-magnet, the liquid leaped up to 

 them when the current was passed, and a 

 little piece of cotton wool saturated with it 

 was strongly attracted. Ordinary air from 

 the room was liquefied in the presence of the 

 audience. A small tube of liquid oxygen, 

 placed in a vessel of air, was put under the 

 air pump, and in a short time liquid air began 

 to condense on its surface. Although the 

 nitrogen and oxygen of the atmosphere are 

 liquefied simultaneously, yet nitrogen, being 

 the more volatile, boils off first, and leaves 

 liquid oxygen behind. This can be proved 

 by holding a glowing taper over a vessel of 

 liquid air ; it does not burst into flame until 

 about four fifths of the contents have evap- 

 orated. Liquid air is magnetic, but more 

 feebly so than liquid oxygen. It is also blue, 

 and the absorption bands in its spectrum are 

 less dark. 



Bohemian Graphite. Natural graphite 

 occurs usually in masses and veins in the 

 oldest rocks, like granite, gneiss, mica schist, 

 and porphyry. At Schwarzbach, in Bohemia, 

 it is found in irregular masses in the gneiss, 

 apparently brought there after the formation 

 of the rock, and having been substituted for 

 the mica, of which it in some places takes 

 the foliated texture. Schwarzbach is situ- 

 ated on a grassy plain among the wild moun- 

 tains of southern Bohemia, in the district of 

 Kruman. The mines and surrounding coun- 

 try belong to the immense domains of the 

 Prince of Schwarzenberg. The mines em- 

 ploy eight hundred workmen, and produce 

 from six thousand to ten thousand tons a 

 year. The graphite is mined in shafts sunk 

 one hundred metres or more beneath the sur- 

 face of the ground. Being impregnated 

 with water, it is easily broken into small 

 blocks by the pick. It is sorted by the 

 miner into first and second choice prima 

 and raffinade. These piles are again sorted, a 

 different process being observed with either 

 kind. The prima, which is designed for 

 pencil-making, is sorted by hand, and all im- 



purities and hard particles are removed from 

 it. The raffinade is passed under millstones 

 where a current of water passing carries off 

 all the richest parts, and, giving up the sand 

 and pyrites in a series of pans provided for 

 them, carries the purified graphite into 

 another series of pans. If pyrite is present 

 in considerable proportions, it is burned out 

 by passing the matter in gratings over flame. 



The Waganda. Describing Uganda in 

 the British Association, Captain Williams 

 said that whatever the merits of the coun- 

 try, the people were worth keeping, for they 

 were a wonderful race. The missionaries 

 had done great good, notwithstanding the 

 conflict of religions. The men were fine, 

 well built, and athletic, and the women were 

 active and intelligent. They were not uni- 

 versally black indeed, in Central Africa 

 there was a considerable variety of shades. 

 They had a strange theory of transmigration 

 of souls, which prevented the people from 

 utilizing the food supply that lay before 

 them. The people were simply dressed; 

 the women were not allowed to wear white 

 cloth, while the men wore white if they 

 could get it. They wore " bark cloth," which 

 was stretched out on pegs to the right 

 length. The Waganda were polygamists, 

 each man having seven wives. The women 

 were very happy, and did the hoeing and 

 other agricultural work, while the men 

 built the houses and carried the food. A 

 man as a rule bought his wives. In one case 

 he met a man who had bought a wife for 

 four cows. He had paid two of the cows 

 and then the lady was eaten by a leopard. 

 He thought it was very hard lines that he 

 should be compelled to pay the remaining 

 cows. The houses were, as a rule, mere 

 slight, temporary structures, but the house 

 in which the late King Mtesa was buried was 

 a wonderful structure with twenty feet or 

 more of thickness of thatch. The churches 

 both Catholic and Protestant were ex- 

 tremely fine, but the former had unfortu- 

 nately been burned. The cruelties of the 

 people had been much exaggerated, and 

 were not comparable to the atrocities which 

 were once committed. In former days a 

 king had all the people killed who passed 

 along a certain road from morning to night, 

 and a man's life was almost worthless. The 



