FA 
A. D. Bache on Gulf Stream Explorations. 208 
bands and ridges simultaneously disappear south of Cape Flor: 
ida. The phenomenon is moreover strikingly exhibited in the 
longitudinal section of the bottom, in connection with the lower 
temperatures. 
e shallowness of the Stream in the strait of Florida, con- 
nected with the fact that the bottom falls off rapidly to the north 
and south afforded an excellent opportunity for testing the ques- 
tion. If the cold water of the under polar current follows the 
bottom, it should appear in the shallow part of the strait, and 
here the warm water of the surface, and the cold water of the 
bottom, would approach each other. Diagram No. 1 shows the 
curves of 40°, 45°, and 50° (bottom temperatures) along the 
eepest part of the stream, commencing at San ook, and run- 
hing as far as the Tortugas. All these curves rise with the bot- 
tom and pass over the ridge which divides the bed of the Atlan- 
tic from that of the Gulf of Mexico, and again fall with the slo 
of the bottom towards the Gulf. In the narrowest part of the 
sttait where the depth is three hundred and fifty fathoms, the 
aa from the surface to the bottom, ranges between 80° 
an 9° 
On the effects of pressure on Saxton’s deep sea thermometer.—In the 
exploration of the Gulf Stream, the temperatures below one hun- 
thoms have mostly been determined by Saxton’s metallic 
amongst themselves, and have agreed well with the indications 
of other thermometers, yet it was thought advisable to determine 
n's thermometer consists essentially of a compound rib- 
bon of silver and platinum fused and pressed together by rollers. 
; n is wound in a spiral form, one end of the spiral 
being firmly fastened to an interior solid axis and the other left 
tes Upon the free end is placed an index arm which moves 
‘vet a circular graduated scale carrying with it a friction hand 
er indicator which is left at the extreme point of the arc reached 
by the true index. The instrument is enclosed in a case to 
Which the water is freely admitted. A variation of temperature 
mapa noticed, as the effect is to give a rotary motion to 
index, 
ae experiments to determine the effect of pressure were made 
Mr 4 Tequest by Mr. J. M. Batchelder with means devised by 
a, auomas Davison at the Novelty Iron Works. The follow- 
ing oe of the apparatus employed, is given by the last 
imed gentleman, ; 
“ti The gauge consists of a brass cylinder H, about eight inches 
38 into which a steel plunger is fitted, the upper part of the 
Pit at A being -70 of an inch in diameter, and the lower at 
‘786, so that the difference in area of the ends is equal 
