40 REPORT OF THE SECRETARY. 



the printing part of the machine, and a record is made in the form 

 of an ascending curve on the drums and on a slip of paper in figures, 

 on the principle of the printing telegraph. When the mercury falls the 

 motion of the pencil is reversed by bringing into operation a second 

 electro-magnet by which is traced a descending curve. Two drums are 

 used, one giving the curve for two weeks and the other the same more 

 developed for two days, the one serving as a check on the other. An 

 interesting series of observations furnished from the United States engi- 

 neer depot at Willett's Point, New York, by General Abbot, exhibits 

 the almost perfect parallelism of two curves for nearly a month, one 

 by an apparatus similar to this at Albany and the other at Willett's 

 Point, from observations with an ordinary standard barometer, the 

 distance between these places being upwards of a hundred and fifty 

 miles. The parallelism of these curves exhibits not only the probable 

 accuracy of the self-recording apparatus, but also the extent in a north 

 and south direction of a wave of atmospheric pressure. The great 

 improvement in meteorological data must depend in future on the intro- 

 duction of self-recording instruments, especially at important points. 



Beside the contributions made directly from the ordinary observa- 

 tions of the Institution, the following is an acccount of a memoir belong- 

 ing to meteorology, previously noticed under the head of publications : 



On the evening of July 20, 1880, a meteoric fire-ball passed over the 

 northern parts of the United States and the adjacent parts of Canada, 

 of so extraordinary a brilliancy as to attract the attention of numerous 

 observers along its entire visible track of nearly 1,300 miles. The phe- 

 nomenon was of so interesting a character that the Smithsonian Insti- 

 tution made exertions to collect observations in regard to it from its 

 meteorological observers and other correspondents, which, together 

 with accounts from newspapers and other sources, were placed in the 

 hands of Professor Coffin, of Lafayette College, for the determination of 

 the orbit of the meteor. In order to correct the observations, in cases 

 where instruments could not be obtained, Professor Coffin directed that 

 estimates should be made of the position of the meteor, by means of an 

 extemporaneous quadrant, consisting of a graduated paper attached to 

 a board, from an angle of which a small plumb-line was suspended. 

 The edge of this instrument being directed to the place in the heavens 

 where the meteor was seen at its greatest elevation, gave approximately 

 the angle of altitude. The meteor was first observed moving from a 

 point over the westeru shore of Lake Michigan, though it is not improb- 

 able that it became luminous when it was somewhat further west, as the 

 sky in that region was obscured by clouds, and it was not until it had 

 reached a point 150 miles further east that the first reliable observation 

 of its position was made; from this point many eyes watched its course, 

 until it disappeared out at sea, in a southeasterly direction, beyond the 

 island of Xantucket. Whatever may have been the orbit of this meteor 

 before it became visible, it is obvious that the portion of the path that 



