772 SEC. 15. GEOGRAPHY. 



The apparatus now submitted supplies this want, and also enables the tem- 

 perature at different depths to be ascertained very easily by a single immersion 



The principle is this : 



Two points, and 20, are accurately marked upon a small thermometer tt 

 (Fig. 1) c 8 cm long. 



If its tube be filed at a given point O), it will easily break there. A 

 column of mercury, length = xy, will therefore remain in the broken part 

 of the tube. By the outer pressure of the atmosphere, this column will be 

 slightly forced into the tube. If the tube is afterwards exposed to another 

 temperature, the variation resulting therefrom, as affecting the length of the 

 mercury column, will be almost imperceptible. To ascertain the temperature 

 at the time of rupturs, it is calculated upon a scale where the distance CD is 

 divided into 20 equal parts. Each part, therefore, will indicate the length of 

 a degree. For instance, if it be seen that the point x is placed at + 6, and 

 that the length of the column is = 14 parts of the scale, it follows that the 

 temperature at the moment of rupture was = 14 + 6 = 8. 



To effect the rupture of the tube at great depths without the registration of 

 the thermometer being affected by the outer pressure, often enormous, the 

 thermometer is encased within a metal wrapper, as proof as need be, and 

 which can easily be fastened to the lead line by metal wires M and N, shaped 

 corkscrew-wise. 



After fixing the thermometer with a screw (2), the ball upwards, between 

 the two cheeks (VH), (Fig. 2), the plan of which is seen only from the 

 back, the filing is done at point x, and the top part AB of the wrapper is 

 tightly screwed up. The bottom part D forms a kind of hinge, covered over 

 with an india-rubber pipe to prevent the water penetrating into it. 



The apparatus being sunk at the required depth, sufficient time is allowed 

 for the thermometer to attain the temperature of the surrounding water. 

 A heavy ring is then dropped down the lead line. This ring, following the 

 apparatus through its entire length, strikes the lever CF, which swings, 

 and pressing upon the hinge occasions the rupture of the tube by the sharp 

 end RS, which runs up within the apparatus. 



To prevent the hinge being unduly displaced, it is barred by the screw K, 

 which is removed just as the apparatus is plunged into the water. Likewise, 

 to prevent the tube being broken by any unforeseen shock to the apparatus, 

 it is fixed between two india-rubber strings (V), drawn between the two 

 cheeks which support the thermometer. 



2909a. Seismochronograph, designed by the exhibitor. 



Prof. Dr. von Lasaulx, Royal University, Breslau. 



1 . The instrument is screwed on, inside, to the back of the station regula- 

 tors * in such a manner that the pendulum, when the ball is resting on the 

 plate intended for that purpose, and, consequently the lower arm of the 

 lever is directed downwards, can swing past this latter, but is arrested imme- 

 diately without making any further vibratory motion when the ball is thrown 

 off through concussion, or by shaking, and the lever shifted thereby before 

 the pendulum. 



2. The instrument must be screwed on very firmly to the back partition of 

 the regulator, in order to prevent the possibility of spontaneous action. 



3. By putting up the instrument the eight round recesses designed for 

 receiving the ball when thrown off must be marked according to their actual 

 position towards the regions of the heavens. The best contrivance will be 

 to engrave the letters N., N.B., E., S.E., S., S.W., W., N.W. on the border, 

 so that the section marked N. actually points towards the north. 



* In places where there is a station clock without a case, the instrument 

 must be fastened to the wall. 



