OBSERVATIONS OP LUMINOUS METEORS. ] 75 



at that time, and passes the meridian at ahout 6 h a. jr. But at the time of 

 tho September equinox it is above (and in that of March it is below) the 

 eastern horizon at midnight. As the tendency of the earth's motion is to 

 make five or six times as many meteors (supposing them not to be collected 

 into streams) come from the hemisphere about the apex as reach the earth 

 from that round the antiapex of the earth's way, the altitude which this 

 meteor-apex reaches above the horizon materially affects their horary abund- 

 ance. Small changes of its altitude when the apex is near tho horizon (as it 

 is at midnight) must be much more perceptible in their effect upon the fre- 

 quency of shooting-stars than the same changes occurring when its altitude 

 above or its distance below tho horizon is greater, as it is towards sunrise 

 and sunset. While, therefore, midnight observations are better adapted than 

 those made either at sunrise or at sunset for exhibiting an annual variation 

 of the rate of frequency, a somewhat singular and anomalous result is notice- 

 able in the present table, where the annual maximum and minimum of fre- 

 quency are not so strongly marked in the result of the evening watches as 

 they arc in the morning observations (although the minimum in the first 

 series towards March and the maximum in the latter series towards September 

 are yet both very plainly indicated). Two sufficient explanations of the dif- 

 ference will, however, probably be found in these considerations, that the 

 collection of meteors into irregularly situated streams must disturb their rate 

 of frequency in the evening hours most sensibly when it is naturally small; 

 and, again, that the a.m. observations may have really been made at an 

 average interval after midnight less than that of the p.m. observations before 

 midnight, and that in consequence the meteor-apex was further from the 

 horizon (below it) during the evening observations than it was above it, on 

 the average, during the morning watches. By consulting the special circum- 

 stances of each watch, and applying for the hour when it is kept a ' tabular 

 reduction ' for the altitude of the earth's apex above the horizon, so as to 

 determine the absolute meteor frequency for the hour, with the apex of the 

 earth's way in a level position or situation in the horizon, a real knowledge 

 of the actual scarcity and abundance of shooting-stars at different times 

 throughout the year might eventually be obtained. A table of the kind 

 required does not admit of precise calculation ; but as it can be approxi- 

 mately constructed and applied, the exact time (the middle of the watch) 

 for which an horary frequency of shooting-stars seen and counted collectively 

 has been determined should be recorded with the date of the watch ; and 

 longer watches than two or three hours (at the furthest) should, whenever 

 clear and kept uninterruptedly enough, be divided into two or more inter- 

 vals, over which separate determinations of the mean horary frequency, for 

 the purpose of determining the true or absolute rate of frequency ' reduced 

 to midnight ' in each, should be made to extend. 



Professor Schiaparelli and Padre Denza continue to invite the united co- 

 operation of Italian observers of shooting-stars on a series of nearly weekly 

 morning and evening dates of the year 1877-78 favourable by the moon's 

 absence or for contributing special materials to the Italian Catalogue for 

 observing shooting-stars. At the beginning of this year they circulated the 

 eighth annual pamphlet of directions for this purpose, containing besides the 

 concerted and other general occasions for meteor watching, a list of the 14 

 stations in Piedmont, Italy, and Spain, with the names of their directors, 

 whose connexion with the Association is still zealously maintained. Anions 

 the new contributors whose names appear in the present list, Signor Arcimis° 

 of Cadiz in Spain, is this year one of the active Members of the Italian Meteor- 

 registering Association. 



