HYDROGRAPHY. ,, 



high to allow that there is at least one normal height of barometer from the mark a — of which 

 has been spoken before — to the level of the mercury in the mercury-reservoir, when this latter is 

 lowered down as far as the floor. The mercury-receiver can be placed in a wooding casing, in which 

 it fits exactly. This casing, and the wooden stand by which the apparatus is supported, are screwed 

 on to the table, on which the whole is placed. A spirit-lamp, shaped like a circular box, is used for 

 the heating of the boiling-flask. In the box is an incision to enable it to be put round the brass 

 tube, which is fitted below on the brass-capsule that is surrounding the boiling-flask. The small- 

 water receivers L l} L 2 and Z 3 , of a capacity of 70 cubic-centimetres each, are hung up on a board in 

 fork-shaped springs, from which they can easily be taken out and put into place again. A vertical 

 screen of metal, screwed on to the wooden stand, is fitted between the boiling-flask and the burettes, 

 and a horizontal screen of asbestos between the boiling-flask and the cooling-water receiver, the 

 former to prevent the burettes from being warmed by radiation from the lamp and the air-bath casing, 

 the latter that warm air shan't make its way up round the cooling-water receiver and heat it. Finally 

 a metal screen is fitted between the funnels T 2 and T 3 to prevent pyrogallic acid from flowing into 

 T 2t when it is poured into T v 



When the apparatus is to be used for analysis, water is filled into the bottle which is in con- 

 nection with the cooling-water receiver round C, as well as into the water baths round the burettes; 

 into the water receivers Z t , Z 2 and Z 3 , and into the burettes with their connecting tubes K t and K 2 , 

 on which all the cocks are closed. The threeway cock H shall always be in such a position as shown 

 in the figure when it is closed. 



The threeway cock H shall he in such a position that there is a passage from C to T Iy and 

 H(, is opened. The mercury-receiver is lifted, so that the mercury fills A and C and goes up into 

 7i. H is shut. If then the mercury-receiver is lowered, the mercury will sink and leave a vacuum 

 in A and C. 



The glass tube G is now put down into the water-bottle. U 5 is opened a sufficiently long 

 time to allow G and the side tube to run full of water, which drives the air in these two tubes into 

 A and C. If ff 5 be shut again, H 6 must be opened. The mercury will then rise, and nearly fill 

 the whole space up to H. If H is opened and the mercury-receiver lifted, the air will be expelled 

 through Ti. Next C and A are emptied again by sinking the mercury-receiver. 



The mercury is adjusted to the mark 0, H 6 is closed, and H 5 opened. The sea-water is now 

 allowed to run in, until it reaches the mark b, on which H h is closed. To enable the experimentalist 

 to observe the rising of the water towards b, two small windows, closed with plates of mica and dia- 

 metrically opposite to one another, have been fitted at the upper part of the metal casing round the 

 boiling-flask. As the space between a and b has been measured beforehand, the volume of the 

 water that has beeu sucked in will be known at once. 



H b is opened a little, so that the mercury rises slowly till it is on a level with the bottom of 

 A. This precaution must be observed, as, otherwise, the glass would easily break when afterwards 

 cold mercury made its way into the boiling-flask. The lamp which has two burners, one on each 

 side of the brass tube that surrounds the lowermost tube of the boiling-flask A , may now be lighted, 

 and the boiling out begins. 



The Ingolf-Expedition. I. 2. $ 



