OCEANOGRAPHICAL RESULTS, MICHAEL SARS, 1900. 139 



The slipping propeller of the Reversing Apparatus could 

 be easily regulated by a screw to reverse the thermometer 

 after having passed up any desired distance between ni. and 

 15 m. The thermomètres were generally allowed 10 minutes to 

 assume the temperature of the water- stratum. 



The Water-Samples and the Determination of the Sali- 

 nity and Specific Gravity. Two water-samples were generally 

 taken from each depth examined. One or very often two small 

 samples were taken from all depths in glass bottles each contai- 

 ning 100 cubic-centimetres of water. These samples were taken 

 for Mr. Helland-Hansen to be examined by titration. The 

 bottles were closed with good cork-stoppers, which were driven well 

 down, and afterwards covered with sulphurated paper, tied tightly 

 round the neck of the bottles. Besides these small samples a 

 set of larger samples were also taken from most depths in 

 seltzer-water bottles containing about 500 cubic-centimetres. These 

 bottles were closed with india-rubber stoppers of the ordinary 

 pattern, consisting of a china-lid with an india-rubber ring under- 

 neath, which is pressed against the upper edge of the bottle by 

 a lever. These stoppers are air-tight when closed, and proved to 

 be very good. The bottles had been used for water years before 

 but for the sake of certainty they were all washed before we 

 started, several days in several changes of water which was 

 heated by steam nearly to boiling point. All parts of the glass 

 surface wich were soluble in water would thus be washed 

 away. The bottles were made of ordinary green glass, which was 

 kindly examined by Mr. Martin Knudsen and found to con- 

 tain, such a minute quantity of soluble matter that it may be 

 disregarded as it would hardly be traceable in the sixth decimal 

 place of the specific gravity of the water. This agrees well 

 with my experience, as after nearly a year I have not been able 

 to find a change in the water kept on such bottles, sufficiently 

 great to be perceptible in the fifth decimal place of the specific 

 gravity. 



