2S ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



made at the telegraph bureau at Brest that magnetic and 

 telegraphic disturbances preceded, accompanied, and fol- 

 lowed the apparition, which was a visible but, in fact, only- 

 secondary part of the phenomena. The aurora borealis is 

 in reality a magnetic storm, as defined by Humboldt, and 

 it is only by the study of the changes experienced by ter- 

 restrial magnetism during these apparitions that we shall 

 come upon the true cause of the phenomenon ; moreover, 

 inasmuch as the magnetic disturbances are always recog- 

 nizable long before the appearance of the aurora, we can 

 easily predict the latter. The disturbances of terrestrial 

 magnetism have probably a cosmical cause, and it is impos- 

 sible to study them properly r except throughout the whole 

 world simultaneously. JVouvelles Meteor ologiqnes, p. 36. 



THE CELESTIAL INDICATOR 



Is the name of a pretty piece of apparatus, patented, we 

 believe, by Mauperin, of Paris. It is designed to enable one 

 to determine instantly the name of any star or constellation 

 by simply pointing in its direction with the indicator of the 

 instrument. The apparatus consists essentially of a tripod 

 stand supporting a circular table, which may be inclined at 

 any angle to the horizon. On this table is engraved a map 

 of the stars, and its circumference is divided into degrees 

 and the divisions of the year. From its centre there stands 

 up a column which revolves about its axis, and supports 

 at its top a pointer. This pointer is movable about its 

 centre in a plane perpendicular to the table, while in a hori- 

 zontal direction it carries a second pointer, fixed at the base 

 of the column, and therefore in close contact with the map 

 of the stars. It of course follows that when the upper 

 pointer is directed toward any stars, and the star map is 

 properly oriented for the day and the hour, the lower point- 

 er will then cover the star in question, and its name may 

 be read on the chart. A lantern attached to the table il- 

 luminates the chart sufficiently, so that the whole stand may 

 be carried out of doors and used there with convenience. 

 The indicator may also be used for the inverse process ; that 

 is, for making charts, and, perhaps w r ith advantage, may be 

 employed by observers of shooting-stars and auroras. It 

 might also, at least in principle, be extremely convenient 



