362 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



As to the special work on which I was engaged on this trip, only a 

 few remarks will be added. At each of the stopping places where 

 time permitted I made magnetic observations, determining the deviation 

 of the compass needle from true north, the dip of the dipping needle, 

 and the force of the earth's magnetism. Two of these stations were so 

 near the magnetic north pole of the earth that the dipping needle 

 stood within six degrees of the vertical. We were so far to the east 

 of the magnetic pole that at Umanak the compass needle pointed nearly 

 west. The horizontal magnetic force in these regions is very weak 

 on account of the great dip, so that magnetic disturbances caused con- 

 siderable changes in the needle, a change of four degrees being noted 

 in a single day at one point. For the same reason the ship's com- 

 passes were very irregular. At some of these places magnetic obser- 

 vations have been made by earlier expeditions. A comparison of our 

 results with theirs will aid in the study of the change in the earth's 

 magnetism, which is continually in progress. At several points I also 

 made pendulum observations for the measurement of the force of grav- 

 ity. This force increases from the equator to the poles, and following 

 the theorem of a French mathematician, Clairaut, we are able to com- 

 pute the amount of flattening at the poles of the earth by comparing 

 the force of gravity at different latitudes. The variations in this force 

 also have an important bearing on various theories that have been ad- 

 vanced as to the condition of the earth's crust, and thus far may be 

 said to point to the truth of the equilibrium theory, which supposes 

 that the earth's crust is in a sort of floating condition, and that all 

 general elevations on the surface are high because they are supported 

 by ligter material beneath, and that depressed areas are low because 

 they are heavy. By a well-known law the time of oscillation of a 

 pendulum will be proportional to the square root of the force of grav- 

 ity, so that if we compare the time of oscillation at different places we 

 will obtain the relation of the force of gravity. For this purpose it is 

 necessary to ascertain the time of a single swing within a few mil- 

 lionths of a second, and to accomplish this successfully an elaborate 

 instrumental outfit is necessary. The chronometers used must also 

 be rated by careful astronomical observations. The results of this 

 work will be published in the Technology Quarterly at Boston, and 

 also by the United States Coast and Geodetic Survey, which furnished 

 the necessary instrumental outfit, and with which the writer is con- 

 nected. 



The lecture was fully illustrated by maps and charts, with many arti- 

 cles of Eskimo manufacture, raiment, etc. 



November 27, i8g6 — Regular Meeting. 



President Hammatt in the chair ; four members present. 



The Curator reported the donation by Mr. George R. Putnam of an 



