SCIENTIFIC SUMMARY. 
445 
water quite at the bottom the temperature of the deepest water cannot 
be ascertained with the ordinary instrument. But by his invention,, 
mechanical apparatus made the thermometer turn head over heels directly it 
touched the ocean bed, and discharge all the mercury above a certain level 
into another arm of the tube, where its height could afterwards be 
observed. 
A Fluorescent Eye-piece for the Spectroscope. — M. Lovet has employed a 
spectroscope in which (says “ Silliman’s American Journal,” August 1874) 
a plate of some transparent and fluorescent body is placed at the point of 
the observing telescope, and then viewed through the eye-piece, which is 
inclined at an angle. The fluorescent plate may be made of uranium glass, 
or of thin pieces of glass a short distance apart, containing any fluorescent 
liquid between them. Two lines drawn at right angles on the glass take 
the place of cross-hairs. It is a good plan to interpose a plate of cobalt 
blue glass to cut off the more brilliant portion of the spectrum. If the eye- 
piece is not inclined, the presence of the fluorescent plate does not prevent 
our observing the lines of the luminous part of the spectrum with accuracy, 
but the fluorescent spectrum produced by the plate is then seen but 
poorly. On inclining it, however, the luminous spectrum can no longer be- 
seen, but the fluorescent spectrum then appears very clearly, of a uniform tint 
traversed by dark lines. These lines may be brought to coincide with the 
lines drawn on the glass, and their deviation measured. 
Dr. Carpenter on Deep-sea Temperatures. —Dr. Carpenter, who is known 
to be investigating this subject, read a paper upon it at the meeting of the 
British Association at Belfast. He stated that while a strong surface 
current is flowing into the Mediterranean through the Straits of Gibraltar, 
a deep-sea current is flowing out into the Atlantic below it. The Mediter- 
ranean tended to grow salter in consequence of losing fresh water by 
evaporation. As the remaining water grew salter it also grew heavier, and 
so formed a lower current flowing out through the Straits, whilst lighter- 
and fresher water from the Atlantic was flowing in above. This upper 
current kept the Mediterranean from growing too salt. There were similar 
under and upper currents in the Dardanelles. The former carried the drag 
along so rapidly, and drew the buoy to which it was attached so quickly 
against the upper current, that the sailors could not keep up with it by row- 
ing, and would have lost it but for the aid of a steam launch. In the Atlantic 
the Gulf Stream was a trumpery thing, only forty miles wide between New 
York and England, and not very deep. It had little or nothing to do with 
keeping our climate warm in winter. The bottom of the Atlantic was 
covered to a vast depth with icy cold water, caused by the melting of Polar 
snows and ice. This cold water had a tendency, he believed, to surge up 
on certain portions of the North American coast, where it washed the shores 
of some of the Southern States. A broad, slow, warm current travels up 
the western shores of Europe and Africa ; a swifter cold current from the 
north washes the eastern shores of North America, bringing down with it 
ice and icebergs from the Polar regions. The Caspian Sea was the only sea 
in the world where the rainfall and river supply of fresh water exactly 
balanced the evaporation. This was because it was a closed sea, and had 
dried up to the point where two things balanced each other year by year. 
