340 



NA rURE 



[August i, 1907 



Whv, by the wav, our Continental friends call this range 

 "the Russian chain" is not quite apparent. Russia is 

 still a long wav off, and Japan has rendered it improbable 

 that Russian earth-hunger will ever be able to extend the 

 dominion of the White Tsar, as was once hoped bv his 

 subjects, to the borders of Tibet. The " Yellow Isar the 

 " Bogdo-khan " in Peking, still rules the lands which his 

 ancestors held two thousand vears before St. Petersburg 

 was built, and that his subjects are worthy to administer 

 this dominion is evident from what Dr. Stem tells us of 

 the civilised rule of the Chinese, and of the constant 

 friendliness of the Imperial authorities to his mission and 

 their keen interest in his archsological discoveries. The 

 thanks of Western science are due to the Chinese for their 

 ever-ready help to Dr. Stein, without which his discoveries 

 would have been impossible to achieve. -— 



Three holes are bored into the glass plate, by means of 

 which the two tubes R and R' and the tap at the bottom 

 are attached. The lube R is connected by means of the 

 glass apparatus, I'ig. 3, with the receiver, and R with a 

 second pump which serves for preliminary exhaustion. 

 The tap is for introducing mercury into (he pump and also 

 for emptying it. The auxiliary pump may 

 injector or any other suitable form of pui 



water 

 'hich is 



NEW HIGH VACUUM PUMP. 



NO laboratory, either chemical or physical, can be 

 carried on' to-dav without a vacuum pump of some 

 form or other, and i'n many laboratories it is essential 

 that the pump shall be capable of producing the very 



capable of giving a vacuum of from 15 to 20 mm. 

 is the porcelain drum which is attached to the axle A. 

 passing through the casing by means of an air-tight joint, 

 to which is attached the driving wheel. 



In using the pump, exhaustion up to 15 to 20 mm. 



hiahest degree of evacuation. Not only is it necessary to 

 be able to produce a high vacuum, but it is also eminently 

 desirable that it should be possible to produce the state of 

 evacuation as rapidly as possible. 



The new high vacuum pump of Dr. Gracde, manufac- 

 tured by E I.eybold's Nachfolger, Cologne, would appear 

 to meet these desiderata. It is claimed that with this 

 pump the highest vacua vet obtainable are secured in a 

 minimum of time. The pump is also simple and compact, 

 and may either be mechanically or hand driven. 



The pump which is illustrated in Fig. i consists of an 

 iron vessel, half filled with mercury, in which a porcelain 

 drum divided into three chambers rotates. When the drum 

 is rotated the chambers into which it is subdivided arc 

 filled alternately with air and mercury. In the hrst place 

 the chambers suck the air from, the receiver, and during 

 further rotation the air is expelled and its place taken by 

 mercury. Fig. 2 shows a section of the pump, one-fourth 

 the actual size. G is the cast-iron casing, which is glazed 

 inside and is cast on to a strong base. The front of the 

 pump consists of a thick plate of glass cemented into the 

 frame P. It is then screwed tightly on to the frame 

 against rubber rings, in order to make an air-light joint. 



is first produced bv means of the auxiliary pump; the 

 drum is then slowly rotated in a direction contrary to the 

 hands of a clock. The space W thus increases in size 

 and air is sucked through the opening L. As rotation is 

 continued the opening L passes below the level of the 



NO. 1970, VOL. 76] 



