MAGNETIC OBSERVATIONS 307 



INCIvINATlON 



Instrumbnt and Mbthods 



Observations for dip were made, as already stated, with the United States Coast and Geo- 

 detic Survey Cassela dip circle No. 5676. For the various standardization observations before 

 and after the work of the Expedition see pages 11 and 12. The instrument was mounted in 

 the observing hut on pier D (figure 2) September 28, 1903. Except for observation and clean- 

 ing and use at the Italian magnetic station on June 6, 20, and 27, 1904, it remained undis- 

 turbed. On the last three occasions it was returned to its pier immediately after the comple- 

 tion of the observations. 



During the winter the needles were turned on the agates by means of wooden pliers. 

 Proximity of the hand produced condensation which froze on the needles ; this appeared, 

 though slight, even while the blades were being rubbed with several thicknesses of tissue 

 paper. Ice crystals continually formed on the instrument, and the frosted roof contributed a 

 constant downpour of fine particles. A linen hood, conical in shape, was suspended from the 

 roof and covered the instrument and top of pier D when not in use. About December 22 a 

 paper hood was substituted with better success. 



The bar magnets and four needles were kept outside of the observatory in a canvas-covered 

 box, which is shown on the plat as magnet box No. i. This box was secured to a post about 

 1 . 5 meter from the ground and could be used as a table or shelf on which the needles were 

 magnetized in good weather. During the winter, when light and weather were both unfavor- 

 able, the needles were magnetized in the west end of the observatory. The bar magnets were 

 returned immediately after the operation to magnet box No. i. 



On October 5, before commencing observations, needle 3 was observed upon, while decli- 

 nation magnet No. 4 was reversed several times at its stowing place. Needle 3 was kept oscil- 

 lating in the magnetic meridian. The same operation was repeated on two subsequent occasions 

 during the winter. On June 7 the same observation was again made, and also with the needle 

 in the magnetic prime vertical. In all these observations no effect was detected on the oscil- 

 lating dip needle. 



A small adjusting pin was kept in a vertical hole on pier D. As it was necessary to use 

 this pin to unloosen the stops on the horizontal circle before observing, the fact of its removal 

 before each day's work is not noted. During the dip observations it was placed on top of the 

 east window (south end). The needle not being observed upon was kept on the north end of 

 the east plate of the observatory. 



Time was noted by watch P, which was always hung on the middle stud of the south wall 

 of the hut. On one occasion, November 30, chronometer Negus 1809 was used and was placed 

 at foot of pier ^7/ against the north side. 



Observations were made after the order prescribed for use in the field operations of the 

 United States Coast and Geodetic Survey. This observing scheme is indicated by the follow- 

 ing specimen set taken at random from the Teplitz Bay series : 



