214 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



the time of oscillation of the lever remained fixed at 408 sec- 

 onds, within a few tenths, daring more than a year. The 

 numerical result of the new and numerous determinations 

 made with the improved apparatus agreed closely with those 

 previously obtained by the authors, and gave 5.56 as the 

 mean density of the earth. They also call attention to the 

 errors in Baily's results caused by the resistance of the air; 

 and, allowing for this, they compute the density from his data 

 to be about 5.55. 



Stanley has proposed the use of the pendulum for the pur- 

 pose of registering cumulative temperatures, or pressures. 

 The pendulum consists of a steel cylindrical tube 32 inches 

 long and If internal diameter, closed at both ends, to the 

 upper of which is attached a rod to connect the pendulum 

 with the clock-work. An air-tight division is placed across 

 the tube at five inches from the upper end, from which a 

 small tube extends to the bottom. Through a screw-hole 

 in the lower end mercury is poured into the small tube, fill- 

 ing both it and the upper chamber. It is then boiled and 

 inverted, and thus constitutes a steel barometer. To con- 

 vert it into a thermometer a small air-hole in the outer tube 

 is closed air-tight. Since by increase either of pressure or 

 temperature the mercury rises in the tube, the centre of os- 

 cillation of the pendulum changes, and its rate is accelerated. 

 The clock is arranged to count beats in units up to ten mill- 

 ions, and the number of beats per day, week, month, or year 

 becomes the unit of temperature or pressure for the period. 

 The upper chamber contains a conical plug for the purpose 

 of automatically effecting certain corrections, especially that 

 due to the expansion of the case. For a pressure apparatus, 

 which the author calls a chronobarometer, the external tube 

 is dispensed with, except at top and bottom. 



According to Nature extensive preparations were made at 

 the Champ dc Mars, in Paris, for producing Foueault's pen- 

 dulum experiment on an extended scale. The weight of the 

 pendulum was 300 kilograms, and the iron wire which sup- 

 ported it was sixty-five to seventy meters in length. It was 

 supported above a grooved pipe moving freely on an axis in 

 its centre. In oscillating, the pendulum displaced this pipe, 

 which, like the pendulum itself, remained iixed in space. Be- 

 neath the pendulum a large terrestrial globe twenty-five or 



