INVESTIGATION OF BALTIC SEA AND GERMAN OCEAN. 289 



between this table and the previous one, for 1869, demonstrate the in- 

 equality of the course of the temperature during the isolated years, and, 

 further, that in the water, as in the air, the climatical differences are rep- 

 resented. Herein the extreme values of the temperatures of the air play 

 a significant part. The following numbers may give an idea how ttie 

 cold year of 1871, with its low temperatures, influenced the temperatures 

 of the water even at great depths : 



Kiel. 



Month. 



1871. 



Jantiary 



February 



March 



April 



May 



June 



July 



August 



September 



October 



November 



December 



Atmosphere. 



Mas. Min 



37.4 

 50.0 

 56.3 

 55.8 

 74.3 

 79.2 

 76.8 

 81.5 

 77.0 

 61.2 

 45.3 

 39.2 



5.0 

 -6.7 

 25.2 

 29.7 

 34.9 

 41.4 

 51.8 

 50.0 

 40.1 

 30.4 

 28.4 



5.7 



Surface. 



Max. Min 



32.9 

 34.2 

 42.1 

 46.8 

 54.5 

 65.7 

 68.0 

 73.6 

 65.7 

 54.5 

 47.7 

 37.6 



33.3 

 32.0 

 35.4 

 38.7 

 45.5 

 53.4 

 59.0 

 61.2 

 56.7 

 47.7 

 39.8 

 34.2 



rive fathoms. 



Max. 



Min. 



27.9 

 31.5 

 34.9 

 37.1 

 41.0 

 51.1 

 55.6 

 59.0 

 57.4 

 50.0 

 41.0 

 35.4 



Sixteen fathoms. 



Max. Min. 



32.7 

 34.2 

 35.4 

 37.2 

 41.0 

 43.9 

 43.9 

 54.5 

 56.7 

 56.7 

 54.5 

 46.6 



30.4 

 32.0 

 34.2 

 34.9 

 37.6 

 41.0 

 42.1 

 44.3 

 55.6 

 54.5 

 47.7 

 38.7 



The low temperatures of the air during a severe winter, therefore, 

 reduce the temperatures of all strata considerably below the usual 

 average. These lower temperatures are maintained in the depth for a 

 long period; in the following autumn they again suddenly increase. If 

 then a mild winter follows, the higher temperatures remain for a longer 

 time and keep the lower strata above the average values. The lowering 

 of the temperatures of all the strata below 32° F. finds an explanation 

 in the fact that the maximum density of the water of 2 p^ cent, salt, 

 as at Kiel, is in the region of the point indicating 29^.8 F., and, therefore, 

 vertically descending currents of the heavier water will effect a rapid 

 equalization of temperature. This will be the more easily possible when, 

 like in the winter months, all water-strata have an increased percentage 

 of salt, with little variation between the different strata. If, however, 

 the lower strata are considerably richer in salt than the upper, then the 

 communication of the lower temperature of the latter will be slow, 

 since the increased densities of the cooler upper strata do not reach the 

 densities of the lower strata, notwithstanding the higher temperature 

 of the latter ; violent winds, however, would soon cause a thorough in- 

 termingling. The above-mentioned sudden changes of temperature in 

 August and in autumn may be attributed to two different causes : either 

 the strata mingle thoroughly, whereby the percentage of salt of the 

 lower strata will be diminished and the temperature of the upper strata 

 communicated to them ; as, for instance, in 16 fathoms at Kiel, September 

 8, 1870, the specific gravity was 1.0167; temperature, 50° F.; September 

 13, specific gravity was 1.0155; temperature, 61o.2 F.; or a sudden 

 entry of heavy underwater from the German Ocean, with its own higher 

 19 F 



