462 TRANS. ST. LOUIS ACAD. SCIENCE. 



yard fence (in a S.E. direction). The declination here agrees very well 

 •with the numerous other values determined around St. Louis, but differs 

 1° 30' from the value at the previous station, about 5 miles distant. Pola- 

 ris observation. 



Station 100 — Florissant, St. Louis Co. Lat. 38° 47'; Ion. 90° 17'. In 

 the yard of Henry Aubuchon, who lives in the edge of the village on the 

 St. Louis rock road. Station S4 ft. E. of the centre of the St. Louis road, 

 and 194 feet from the centre of the street N. of the yard. Polaris observa- 

 tion and morning elongation. 



Redetermination of the Temperature constant {q) for Mag- 

 net Cg. 



This quantity was determined in March, 1S79, but at that time 

 the facilities at hand made it a matter of great difficulty to secure 

 accurate results. It was necessary to remove the deflecting mag- 

 net in order to determine the angle of deflection, as at that time 

 a second instrument was not available. 



The redetermination was made in the basement room ^elow 

 the physical laboratory, known as the "clock room." Two solid 

 brick piers set well into the ground served to support the instru- 

 ments. The magnetometer was mounted on the south pier, with 

 needle Cj^ suspended and Cg deflecting. Declinometer No. 3, 

 with magnet No. i suspended, was mounted on the north pier» 

 and served to determine the corrections for hourly change in 

 declination. The scale values of the suspended magnets are, C17, 

 z'.gg ; No. I, I'.Qo ; and the scales are so mounted that when the 

 easterly declination increases, the scale reading of No. i increases, 

 while that of C^^ diminishes. 



Both magnets had been suspended for a week. The suspend- 

 ing fibres were examined for torsion just before the series began. 

 One had 5 degs. of twist, which was corrected, while the other 

 was without torsion. 



At 2 o'clock P.M. of the nth of October, 1881, the scales read 



Cj7 79.0 I No. 1 77.95 



At 3 P.M. magnet Cg was put in place deflecting C^^, its centre 

 being 21 inches west of the zero point of the deflection bar, with N. 

 pole west. It was surrounded with a jacket of ice- water which was 

 fed by a drip of ice-water during the next night. The next morning 

 the readings of the needles were taken as follows : 



