DEEP-SEA EXPLORATION. 
325 
oljlltci'ation. The partoftlie stem wliicli forms the hackgroiiud to the graduations is enameled white 
to give distinctness to the mercury. 
To make this instrument availahle for deep-sea use it is necessary to provide some reliable method 
of turning the bulb upward at the proper time; also, to prevent it from tnrniiig down ag.ain before 
the surface is readied and the temperature read. 
Plate XX shows a metal frame devised by Coimiiaiider Magnaglii of the 
Italian navy. It is described as follows in an advertisement of Messrs. Negretti & 
Zambra : 
Negretti <f’ Zamhra's patent improred frame standard deep-sea thermometers . — A is a metallic frame in 
which the case 15, containing the thermometer, is pivoted upon an axis H, but not balanced upon it. C 
is a screw fan attached to .a sjiindle, one end of which works in a socket 1), and on the other end is 
formed the thread of a screw E, about half an inch long, and just above it is a small pin or stop F, 
on the siiindle. G is a sliding top-piece, against which the pin F imjdnges when the thermometer 
is ad justed for use. The screw E works into the end of the case B, the length of play to which it is 
adjusted. The number of turns of the screw into the case is regulated by means of the iiiu .and stop- 
piece. The thermometer in its case is held in position by the screw E and descends into the sea in this 
position (lig. 1), the fan C not acting during the descent because it is checked by the stop F. When 
the ascent commences the fan revolves, raises the screw E, and releases the thermometer, which then 
turns over and registers the temjierature of that spot, owing to the axis II being below the centerof 
gravity of the case B as adjusted for the descent. Each revolution of the Ian reiiresents about 2 feet 
of movement through the water, so that the whole play of the screw requires 70 or 80 feet ascent; 
therefore, thespace through which the thermometer shoulil pass before turning over must be regulated 
at starting. If the instrument ascends a few feet by reason of a stoppage of the line while attaching 
other thermometers, or through the heave of the sea, or any cause whatever, the subsequent descent 
will cause the fan to carry back the stoj) to its initial position, and such stoppages may occur any 
number of times ]>rovided the line is not made to ascend through the space necessary to cause the 
fan to release the thermometer. 
When the hauling in has caused the turn-over of the thermometer the lateral sjuing K forces the 
spring L into a slot in the case B and clamps it (fig. 3) until it is received on board, so that no change 
of position can occur in the rest of the ascent from any cause. 
The case B i.s cut open to expose the scale of the thermometer, and is also ])erforated to allow 
free entry of the waiter.” 
The Magnatflii frame above described is a great improvement on tlie wooden cases 
formerly farnisbed by tbe makers, but even tliis did not iirove entirely satisfactory 
in all respects, inasmuch as it could not be secured to sounding wire, and could not, 
therefore, be used in series. The fan failed to act occasionally, and the springs K and 
L were apt to hold the case B in a vertical position by friction, thus preventing the 
turn over at the proper time. 
This tbermometer was first used by the Fish Commission in 1877, when it was 
mounted in a wooden case about 13 inches in length, secured to the lead line by a 
lanyard at the bulb end. A cylindrical cavity contained a quantity of shot, movable 
from end to end, suflicient to nearly overcome its buoyancy in sea water. On sending 
the case down the friction of the water, aided liy the buoyancy of the case, tended to 
keep it upright and bulb down in the water, the shot rolling promptly to the lower 
end of the cavity. Eeversing the motion and hauling in the line the case was capsized 
and the shot run to the other end, tending to keep it down and the bulb uppermost. 
This arrangement answered its purpose at moderate depths in smooth water 
where veering and hauling of the lead line could be made continuous, but the motion 
of the vessel iu a moderate seaway was suflicient to capsize it again and again, and 
the case lost its buoyancy in about 000 fathoms, the wood becoming waterlogged. 
Many attemiits were made, both in this country and in Europe, to imiirove the case, 
and in September, 1880, the writer attached a spring latch to the end opposite the 
