August 10, ISS).] 



SCIENCE. 



157 



No one would undertake to obtain such 

 results with any deep-sea thernioiiieter in use 

 at that time. The Miller-C'assella instrument 

 would utterly tail to record the temperatures 

 at the boltoni ; and, even if it did re- 

 cord them, its readings would not he 

 regarded as within half a dejjree F. 

 of the exael temperature. Tlie Sie- 

 mens electric apparatus, which has 

 been used on the IJlake with great 

 success, cannot be depended upon for 

 greater aecurac3- than a quarter of 

 one degree. 



Capt. G. Rung of the Danish me- 

 teorological institute exhibits some 

 thermometers enclosed within thick 

 layers of cork, only the scales being 

 exposed to view. In this way it is 

 possible to obtain deep-water temper- 

 atures ; for the instruments can be 

 hauled upon deck, and readings made, 

 before any heat can pass through the 

 cork. This method, however, seems 

 rather primitive ; and, even if practica- 

 ble, it is quite too slow to receive 

 much commendation. 



There can be no doubt that the best 

 deep-sea thermometer is the latest 

 Negretti and Zambra form. rei)re- 

 sented in fig. 1. It is so well known 

 that a full description is not neces- 

 sary ; but as a reminder it may be 

 said, that, when the instrument is 

 upright, the mercury extends up into 

 the tube to a height corresponding 

 to the temperature. If then inverted, 

 the mercury breaks at a particular point in the 

 bend A, and runs down to the other end, 

 where the temperature is read otf. The small 

 quantity of mercnry in the bore does not ap- 

 preciably change its length tor slight variations 

 of temperature. For a long time this has 

 been the favorite instrument for taking deep- 

 sea temperatures singly, but until lately no 

 means had been devised for taking serial tera- 

 l)eratures with it at a single cast. At the 

 fisheries exhibition are shown three new 

 methods of inverting the instrument at a 

 given depth. The first we shall mention is 

 exhibited by Capt. G. Rung of Denmark. It 

 is scareelv worth while to describe this ap- 

 paratus in detail ; for. altiiough it is undoubt- 

 edly an excellent device, the two other 

 methods to be described are much better, 

 because they are lighter and smaller. Capt. 

 Rung inverts the thermometer by sending down 

 a messenger along the line. By causing the 

 inversion of each instrument to fiee a mes- 



senger to invert the next instrument below it, 

 he obtains serial temperatures in the same 

 manner as is done with the new device of Mr. 

 W. L. Hailie, to be soon described. 



Capt. Hung also exhihits a water-bottle and 

 tliermometer combined. A brass cylinder, 

 perforated at the bottom with three small 

 • irilices, has a piston working air-tight within 

 it. Within the piston-rod, which is perforated 

 hiTe and there, is a Negretti and Zambra 

 tliermometer, the bulb being at the outer ex- 

 tremity of the rod. 



To use the apparatus, the piston is shoved 

 in, and the end of the sounding-rope tied to the 

 projecting end of the piston-rod. The appa- 

 ratus is then inverted ; and the lower end of 

 the cylinder, being now u))permost, is secured 

 to a catch a short distance up on the line. 

 In this |)Osition it is lowered to the required 

 dejith, when a messenger is sent down which 

 releases the cylinder. It falls, turns over, 

 and the weight is then transferred to the 

 piston-rod. The thermometer, being now bulb 

 up. registers the temperature ; while the weight 

 of the cylinder causes it to pull the piston-rod 

 out to the fullest extent, and, as the piston 

 rises, it draws the water into the cylinder 

 through the small holes in the bottom. 



In figs. 2 and 3 we have illustrations of the 

 ingenious apparatus devised by Commander 

 Magnaghi of the Royal Italian navy, and 

 exhibited by Messrs. Negretti and Zambra. 

 It will be seen that the propeller-wheel C 

 screws up or down as it revolves. During 

 descent the propeller does not move, as the pin 

 F is against the stop G. On reversing the 

 motion, the propeller screws upward until the 

 screw E releases the case, wliich then turns 

 over, as in fig. 3, and is hold in position by 

 the spring K. 



A still later form of this instrument has just 

 been made, in which the thermometer-case is 

 suspended on trunions at the lower end, in- 

 stead of near the middle. 



Another method for accomplishing the same 

 result has been devised by Mr. W. L. Bailie, 

 U S.X. In his arrangement the case of the 

 thermometer is attached to the sounding-wire 

 by a -cam-catch at the bottom, and by two 

 lateral spring jaws at the top, which encircle 

 the wire. 



A brass messenger is sent down the wire 

 when the desired depth is reached, which 

 opens the jaws, thus releasing the top of the 

 case. The latter then tails over, turning on a 

 swivel at the bottom. A hook at the bottom 

 carries a second messenger, which is released 

 as the case turns over, and falls down to invert 



