MISCELLANY, 



379 



This being the case, there is little or no 

 Circulation — the water becomes to some ex- 

 tent stagnant, affecting in a marked manner 

 the development of life in it. 



Dr. Carpenter was astonished to find in 

 the Mediterranean very few evidences of 

 life at depths greater than eighteen hundred 

 feet. " The dredge," he says, " brought up 

 barren mud," and, however abundant life may 

 be around its margins, its deeper portions 

 are azoic. In the cold but freely-circulating 

 waters of the Atlantic, animals are found 

 at nearly the greatest depths — while the 

 dredge is often filled from soundings of one 

 to two miles. Whence the difference ? "I 

 found," says Dr. Carpenter, " the deep wa- 

 ters of the Mediterranean turbid, filled with 

 fine particles of sediment which at last 

 make the ooze of the bottom." The pres- 

 ence of this floating dust, even near the 

 surface, is proved by the blueness of the wa- 

 ter. Turbidity is known to be unfavorable 

 to the development of many kinds of ma- 

 rine life. Prof. Dana has shown that a 

 small quantity of sediment thrown upon a 

 portion of a reef kills the polyps on that 

 part, and the growth and distribution of 

 coral - reefs are largely determined by this 

 cause. But, another reason for the absence 

 of life at the bottom of the Mediterranean 

 is, the deficiency of oxygen in its waters in 

 those depths. 



Deep waters from the Atlantic and Med- 

 iterranean have been boiled off, and in the 

 gases from the first there was twenty per 

 cent, of oxygen, from the latter only five 

 per cent. But of carbonic acid there was 

 from the first only thirty to forty per cent., 

 while the latter furnished sixty per cent. 

 Here, then, in the abundance of carbonic 

 acid, and deficiency of oxygen, is a possible 

 cause for the paucity of life. 



But whence arises the deficiency of 

 oxygen. Chiefly, perhaps, from the slow de- 

 composition of organic matters, carried in 

 by rivers and other agencies, and which 

 may add to the turbidity referred to. 



This state of things in the Mediterra- 

 nean, and possibly in other inland seas, evi- 

 dently arises from absence of circulation of 

 the waters. Winds disturb the surface 

 only, and Dr. Carpenter says there is in the 

 Mediterranean no thermal circulation — or 

 circulation which arises from inequality of 



temperature. It has been said that ine- 

 quality of density caused by evaporation 

 must produce some vertical circulation of 

 the water, but density from lowering of 

 temperature at the surface never exceeds 

 the density of the deeper waters, and no 

 circulation disturbs or mixes the superim- 

 posed masses. 



The oxygen from the surface can only 

 reach the deeper waters by diffusion, hence 

 its deficiency at considerable depths. In 

 the Atlantic, and doubtless in all open 

 oceans, the waters are diffused, and mixed 

 by a wonderful system of circulation, the 

 dynamic agencies of which are not present, 

 or only in a modified form, in the inland ba- 

 sins. 



The well - known and often - criticised 

 statement of Edward Forbes, that life 

 ceases at a depth of three hundred fath- 

 oms, is confirmed by the researches of Dr. 

 Carpenter, in so far as it relates to inland 

 seas, the researches of Prof. Forbes being 

 in the JSgean. The error consisted in ap- 

 plying the same rule to the open oceans, 

 where a different one prevails, and this ap- 

 pears to have been the error of others rath- 

 er than of Forbes. 



Unequal Power of the Eyes. — Probably 

 there are but few persons possessed of 

 equal power of vision in both eyes. This 

 circumstance, as is observed by a writer in 

 Science Gossip, will doubtless account for 

 some people being unable to appreciate the 

 binocular microscope. The writer in Sci- 

 ence Gossip has a friend who always found 

 difficulty in studying with a binocular, in 

 that he could never get the two glasses to 

 blend. In 1851 he attended the Great Ex- 

 hibition in London, and there his eyes were 

 constantly ranging from short to long dis- 

 tances. After he had left the Crystal Pal- 

 ace he felt that his eyes were very much fa- 

 tigued, and was at a loss to understand the 

 meaning of it. By this and other circum- 

 stances he discovered that there was a focal 

 difference in his eyes. One eye was far- 

 sighted, while the other was wear-sighted. 

 For reading-purposes he wears a pair of 

 spectacles in which the one glass is made 

 for the far sight, while the other is a plain 

 glass, the left eye being raar-sighted, and 

 consequently requiring no aid from specta- 



