November 28, 1884.] 



SCIENCE, 



4*5 



This color gradually formed a uniform sediment of 

 an indefinite tint over the bottom of the basin. On 

 the night of the 26th of December last, which was 

 an unusually cold one for this climate, the water in 

 the basin froze. On the melting of the ice the next 

 day, the beautiful figure you see on the photographs 

 was left in the sediment. I carefully poured the 

 water from the basin, let the sediment dry, and thus 

 perfectly preserved the figure. It has been accurately 

 photographed by an artist in this city. The negative 

 is preserved; and, if you would like to have any more 

 copies, they can readily be obtained. 



"'We are not much accustomed, in this warm 

 country of ours, to the beautiful 'forms of water;' 

 and this has 

 struck me as a 

 little remarka- 

 ble, and wor- 

 thy of being 

 kept.' 



"The fact 

 that the results 

 have been pro- 

 duced by col- 

 ored sediment 

 indicates a 

 method of ex- 

 hibiting the ef- 

 fects of crystal- 

 lization in an 

 interesting 

 manner." 



Professor 

 Tyndall refers 

 to this as a 

 'surprising 

 case of crystal- 

 lization,' which 

 it most certain- 

 ly is. 



Some years 

 ago a glass- 

 crystal 1 i z i n g 

 dish was filled 

 with Ohio-river 

 water, which 

 at certain 

 stages carries 

 in suspension 

 a large quanti- 

 ty of yellow 

 clay, and al- 

 lowed to settle 

 for several 



days, forming a thin yet firm deposit on the bottom 

 of the dish. During a very cold night the water in 

 the dish was frozen, and the sediment figured as 

 herewith represented. The ice was melted, water 

 removed, and the sediment dried. I have this re- 

 markable specimen in my possession to-day, just as 

 it was originally formed. 



Wm. L. Dudley. 



Cincinnati, O. 



An open polar sea. 



In one of your September numbers (No. 86), there 

 was a letter from Lieut. Kay on this subject, which, 

 I think, needs some elucidation. Mr. Ray questions 

 the existence of an open polar sea, on account of the 

 low temperature of the water found by the last Ameri- 

 can polar expedition. What has the temperature of 

 water to do with its greater or less freedom from ice in 

 arctic climates ? The temperature of maximum den- 



sity of sea-water being lower than the freezing-point, 

 the formation of sea-water ice is impeded, as the 

 colder water is not the lighter. If, however, ice forms 

 on sea-water, it is because, 1°, the specific gravity near 

 the freezing-point differs much less (about on^-third 

 as much) from degree to degree than near 70°; so 

 colder water has not so strong a tendency to arrange 

 itself according to specific gravity as warm water, 

 and may freeze, especially with cold winds from the 

 land; 2°, at the close of summer the upper layers are 

 generally much le>s salt than the lower, on account 

 of the fresh water coming from melting ice, and from 

 rivers swelled by the melting snow (this is especially 

 the case in many inland seas of the northern hemi- 

 sphere, and to 

 a less decree in 

 the southern 

 hemis ph ere ; 

 such an ar- 

 rangement of 

 the waters al- 

 lows the upper 

 strata to be 

 colder and yet 

 lighter, and 

 thus is very fa- 

 vorable to the 

 formation o f 

 ice); 3°, after 

 ice begins to 

 form, it in- 

 creases both 

 from below, on 

 account of the 

 cold penetrat- 

 ing the ice, and 

 from above, on 

 account of the 

 freezing of 

 waves, spray, 

 etc., on the 

 surface of the 

 ice. 



Now, when 

 the second con- 

 dition, the most 

 powerful (at 

 least, for the 

 beginning of 

 the formation 

 of sea-ice), is 

 absent, or pres- 

 ent only in a 

 small degree, 

 the conditions for the formation of field-ice or sea- 

 ice are lacking, or only present on a small scale. This 

 is more often the case in the high latitudes of the 

 southern hemisphere than in the northern; because 

 in the southern the seas are deeper and more open, 

 and receive little river- water, the temperature of the 

 air and sea is below the freezing-point to about 62° 

 south, and the icebergs reach that latitude without 

 melting. 



If the north pole is surrounded by open, deep 

 water, and if the temperature of summer there is 

 lower than at the stations where observations have 

 been made in the northern hemisphere (both suppo- 

 sitions will be granted as possible), there do not exist 

 conditions so favorable for the formation of field-ice 

 as on the north coast of Asia and North America, as 

 there will be no brackish water of a low specific 

 gravity near the surface. Thus there may be rela- 

 tively open water near the north pole, not warm,- 



