32 



HYDROGRAPHY. 



pipe at the top. The whole is kept together by two discs of brass, placed respectively on top of the 

 uppermost and below the nethermost India-rubber sheet. Four long screws are fitted between the 

 above-mentioned discs outside the glass cylinder. By means of an India-rubber tube the cooling- 

 water is admitted into the cylinder from a bottle, which is placed in a higher position, and the tubu- 

 lure of which is at its bottom; through the eduction pipe it flows into another bottle, which is placed 

 on the table, on to which the whole apparatus is secured. 



The burettes used for analysis are three glass tubes B l} B 2 and i? 3 , about 40 cm long, and not 

 so wide at the top as below, the diameter at the lower end being n mm , while at the upper end it is 

 only 7 m,n . The upper part is divided into twentieths of cubic centimetres and the nethermost in 

 tenths. The zero-point is marked at the place where the burette and the capillary tube, in which it 

 terminates at the top, meet, and this mark is found exactly by filling the burette and the said capillary 

 tube with water, and allowing air to ascend through this latter; the zero-point will then be exactly 

 at that place where the upper meniscus of an air-bubble appears. The bitrettes £ t and B 2 terminate 

 both at their lower ends in a narrow glass tube, which can be closed by means of a small India- 

 rubber tube with a jam-cock. Close above the narrow part, a side-tube of a small diameter is fitted, 

 which communicates relatively with the two water reservoirs L t and L 2 by means of a long India- 

 rubber hose. On the other hand, the hose leading to the reservoir Z 3 is fitted on the narrow tube 

 in which B i terminates. The burettes B 2 and B 3 are at the top, like B x , continued in the shape of 

 capillary-tubes, but these latter are, in so far as regards the burettes B 2 and Z? 3 , supplied with the 

 cocks 7/ 4 and // 3 , and adopt at the top the shape of the funnels T 2 and T v 



Each of these three burettes is surrounded by a water-bath, consisting of a glass-tube 30""" 

 wide, at the lowermost aperture of which the burettes are inserted through India-rubber stoppers. To 

 facilitate the insertion, the burettes are cut a little above the place, where the uppermost of the lower 

 side tubes is coming out; after the insertion, the two pieces of the burettes are connected again by 

 means of small India-rubber tubes. The water-bath tubes surround also the nethermost part of the 

 capillary tubes, in which the burettes are continued at the top, and they are at that place closed with 

 India-rubber sheets to keep the water-bath clean. Thermometers are inserted into the bath through 

 these sheets. 



The tubes proceeding from the threeway cock //, as well as all other connecting tubes are 

 regarded as capillary tubes; they are all substantial glass tubes with a bore of 2 mm . The side tube 

 from the threeway-cock is by means of an India-rubber tube connected with the one branch of 

 a "T tube, the lower branch of which is led to the upper capillary tube of the burette B z by means 

 of an India-rubber hose. On the third branch of the ~T tube, is fitted a small tube, into which the 

 tube K x with the cock //, is fitted. Between K t and the burette B 2 is another little tube, which 

 is attached to a side tube proceeding from B 2 , a little above the second side-tube, and by which B 2 

 is put in connection with L 2 . In a similar manner, the capillary tube K 2 with the cock H 2 connects 

 the burettes B 2 and B y 



As the air-analysis-apparatus has to be used, even when the ship is in a seaway, it becomes 

 a matter of course that everything must be properly secured, in consequence of which the whole 

 apparatus is screwed on to a wooden stand. The table together with the stand, must be sufficiently 



