140 



HYDROGRAPHY. 



general is greatly heated — as a rule to be smaller than j (-) for the surface-water of the Atlantic. 

 Owing to this, there will be a possibility of the heated surface-layer of the ice-water 

 being able to flow out over the Atlantic-water. If, however, the Atlantic-water has the 

 temperature a b 8°, j(-) will be a h 1-0275, and while the surface-layer of the ice-water in general has 

 s (—) smaller than 1*0275, tne cold layer of the ice-water will often have j(-) larger than 

 this value. We see thus that the difference of specific gravity between Atlantic-water and ice-water 

 will not with any great power try to mix the two species of water together or produce currents of 

 the coldest ice-water. 



That notwithstanding this fact currents must exist, which try to neutralize the difference between 

 Atlantic-water and ice-water, called forth by differences of the specific gravity, can be seen by the s (-) 

 curves appertaining to the stations in section XXIII. Station 46: the s(~) curve is rising a little from 

 o to 100 fathoms (188 M.), and remains thereafter constant with the value 1-0276 until a depth of at 

 least 400 fathoms (753 M.). The stations 134 and 136: the j(-) curves at the two stations are nearly 

 equal, and have in the main the same form as the s(—\ curve at station 46; the value of s(-\ in the 

 horizontal piece of the curve is the same as that applying to the same piece at station 46, but at 

 these stations it only remains constant until a depth of hardly 200 fathoms (377 M.). Station 137: At 

 this station there is no tract through a certain depth where s (j) remains constant ; the curve has only a 

 turning-point at the place, where j (-) has the same value 1-0276 as this quantity had at the constant 

 pieces of the curves at the stations 46, 13431:^136. We see therefore that the different forms 

 gradually merge into one another at the line of demarcation between Atlantic- 

 water and North-Ocean-water, and it must therefore be supposed that there are local 

 currents at this boundary with the object of neutralizing the differences of specific 

 gravity for equally large depths in the two species of water. 



TEMPERATURE AND SALINITY AT THE BOTTOM. 



It will be seen from plate XXXI of the chart representing the temperature and salinity at the 

 bottom, that the drawn isotherms and isohalines have nearly the same course, and without any appre- 

 ciable difference follow the bottom-curves. In the mean time it is entirely out of the question 

 that there can be a complete similarity between the course of the two said curves and that of the 

 bottom-curves; if this should be the case, isotherms and isohalines would have to be horizontal planes, 

 which, according to the plates XX — XXIX, is far from being the case. The chart shows that the 3 

 and 4 isotherms are running parallel with the ridge extending from the south-western extremity of 

 Iceland, and that a 3° isotherm is enclosing the deepest of the basin of the Denmark Strait, which 

 likewise applies to the 35.10 isohaline. 



Nearly all the isotherms are coming into close proximity of one another northwest of Iceland, a 

 circumstance which appears from the observations at station 15 and 99, which are close to each other. 

 Station 15: temperature at the bottom — o°8, depth 330 fathoms (621 metres). Station 99: temperature 

 at the bottom 6°i , depth 187 fathoms (352 metres). It is perhaps the great difference of depth that 

 is the cause of the great difference of temperature between the two stations, but it must not be left 



