9G ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



A NEW SEISMOMETER. 



A seismometer devised by Malvosia, of Bologna, is thus 

 described : On a slightly inclined board is fixed a spherical 

 cap, having eight grooves corresponding to the eight princi- 

 pal points of the compass. A little beyond the edge of the 

 cap there is a projecting wooden ring which limits the in- 

 clined surface. On the top of the cap is poised a little brass 

 ball slightly flattened at the point of contact. Upon the 

 ball rests very lightly a conical weight, by a small screw 

 projecting from its base ; which weight is suspended by a 

 chain from an overhanging arm, movable up and down on 

 a support at the side. The least shock will make the ball 

 topple over. When it does so, it runs down one of the 

 grooves of the cap to the inclined plane, at the lower part 

 of which it finds a hole, and, passing into it, causes a gun to 

 be fired off. After the ball leaves its position on the cap, a 

 spring needle, longer than the diameter of the ball, shoots 

 out from the little conical weight that rested on the ball, 

 and catches in that groove of the cap down which the ball 

 has run. Thus the direction is indicated from which the 

 shock came. The instrument can be made very sensitive. 

 It differs from that recently introduced by La Saulx into the 

 earthquake stations of Prussia, principally in that the appa- 

 ratus does not of itself record the exact time at which the 

 shock took place, but merely calls the attention of the ob- 

 server by means of the discharged gun. By combining the 

 instrument of La Saulx with the simple upright pillar seis- 

 mometer as described by Mallet, observations could be ob- 

 tained which would be of more value than those given by 

 the seismometer of Malvosin. Journal of the Franklin In- 

 stitute, A2)ril,lSl 5, 243. 



THE MAGNETIC DECLINATION AT ST. PETERSBURG. 



The lonor series of observations of magnetic declination 

 that has been accumulatino; at St. Petersburg during the 

 Last 150 years has been subjected to a very full study by 

 Mielberg, of that city, who has taken especial pains to ex- 

 amine the accuracy, reliability, and even genuineness of the 

 observations, and to correct them for such sources of error 

 as can be appreciated. The independent observations made 



