374 eepokt -1878. 



fireball seen by every new observer appears to him in a different part of 

 the sky, or virtually as another meteor, it follows that both for fireballs 

 and for very scanty meteor showers the multiplication of observers of 

 the phenomenon by increasing the number of meteor tracks belonging to 

 the same radiant-point, suffices, when they are sufficiently exact and 

 numerous, to fix its place exactly, and to determine the direction from 

 which the meteor shower or the fireball took its flight. Exactness in 

 describing a fireball's apparent path by the stars or otherwise is the more 

 desirable and important, because no doubt exists that any tico such re- 

 corded appearances of its path must belong to the same meteor ; and that, 

 therefore, when prolonged backwards to their intersection, if they are 

 fairly accurate they will be sufficient by themselves to point out its 

 radiant-point or the direction and distant origin of its real course with 

 satisfactory precision. But even a dozen meteors of a poor and scanty 

 star-shower only afford presumptive evidence of their having a common 

 direction and radiant-point at the centre of divergence of their tracks, 

 as scarcely any other evidence but this divergence, in general, exists of 

 their belonging to a common system ; and to increase its probability a 

 fresh number of meteors of the same shower must be noted, and must be 

 traced back to the same centre of divergence. Observations of sporadic 

 shooting-stars must, therefore, be greatly multiplied (however accurate 

 they may be), while two accurate observations only of a fireball are 

 absolutely necessary to determine the exact direction, together with the 

 height and distance, and the other particulars of its flight. This fortunate 

 concurrence of two or more simultaneous observations is sometimes 

 recorded of a shooting-star ; and then the real direction of this meteor 

 is as certainly determined as that of a fireball, and the orbit of either 

 (which is the sole clue that we can gain to its astronomical history) is 

 known as certainly as the orbit of a meteor stream. But such accuracy 

 of observation as would allow us to depend upon two observations only 

 is seldom, if ever, reached by observers, either of shooting-stars or fire- 

 balls, and of the latter class of meteors especially, many scores of accounts 

 are annually indited by unpractised observers, containing no material 

 data (or only conflicting ones) of the meteors' courses, while the 

 accordant notes occasionally furnished of shooting-stars by well-skilled 

 observers show the difficulty, if not the hopelessness, of arriving by two 

 observations at anything approaching to the accuracy of instrumental 

 determinations. With rare exceptions, therefore, a large and abundant 

 collection of observations is needful for exact comparisons, which it is the 

 object of the Luminous Meteor Committee appointed for this purpose by 

 the British Association to obtain, by providing observers with suitable 

 forms of registry, maps, and instructions for recording the appearances 

 of fireballs and ordinary shooting-stars. The Committee distributes to 

 observei's who apply for them printed Forms of Registry and Directions, 

 as the most convenient and efficient means of assisting them in systematic 

 observation. For the best means of noting and describing exactly the 

 appearances of large meteors the Committee also directs attention to a 

 letter in the ' Scotsman ' (daily newspaper) of May 1st, 1878, by Professor 

 Herschel, from the full paragraphs of which, pointing out the features 

 of position and appearance to be recorded, it is not necessary to repro- 

 duce here a long series of appropriate suggestions, as instructions for 

 recording large meteors and ordinary shooting-stars will be found 

 sufficiently illustrated in the Committee's printed Forms of Registry and 



