358 Prof. C. Piazzi Smyth's Meteorological 



reference to ** luminous meteors," and by the British Association, 

 in the matter of the aurora borealis. Uniformity and sufficiency of 

 observation are extremely necessary to be attended to by all who 

 undertake these subjects, and they only have to write, it seems, to 

 Prof. Baden Powell, at Oxford, or to Prof. Phillips, at York, for 

 copies of the forms. The following is an enumeration of the sub- 

 jects to be attended to in regard to tables : — 



Observations of Luminous Meteors. * 

 1, No. ; 2, date ; 3, hour; 4, place; 6, appearance of magni- 

 tude ; 6, brightness and colour ; 7, train or sparks ; 8, velocity or 

 duration ; 9, direction or altitude ; 10, general remarks ; 11, 

 observer; 12, reference. 



Simultaneous Observations of Aurora Borealis.^ 



Place Lat. N Long. W.- Elevation above the sea in feet 



1, Day, hour, and minute, by Greenwich mean time ; 2, defini- 

 tion of the object specially observed, as arch, beam, corona, or point 

 of convergence of streamers ; 3, position of the object by stars ; 

 4, position of the object in altitude and azimuth, by instruments ; 



* Directions. — No. 3. Under the head " Hour," state Greenwich mean time if 

 known ; if not, what time is meant. No. 4. Give the latitude and longitude of 

 the place of observation. No. 6. Compare with magnitude of stars ; or with 

 the apparent brightness or diameter of planets, the moon, &c. No. 6. State 

 whether the brightness increased or decreased during the appearance. No. 7. 

 Distinguish the kind of train ; whether continuous or broken; whether a real 

 train, or only an optical impression, &c. No. 8. If possible, give the difference 

 of hour, minute, and second appearance and disappearance. No. 9. The direc- 

 tion as compared with any known fixed stars ; or the altitudes, or if possible, 

 the right ascension and declination of the points of appearance and disappear- 

 ance, or at least the points of the compass. 



t Notes. — 1 . Auroral phenomena have been found most frequent between the 

 hours of 7 and 12 p.m.; the greatest number at 9, or soon after. Itis recommend- 

 ed that at every 10th, 20th, 30th, &c. minute of Greenwich mean time (as 80, 

 8-10, 8-20, &c.), the definition and position of arch, beam, or point of convergence 

 (as being most suited to measurement and likely to be recognised at distant 

 places), be recorded in columns 2 and 3, or 2 and 4 ; and that at the 5th, 16th, 

 25th, &c. minute, the state of the magnetic needle be recorded in column 5 ; the 

 other minutes being left to be employed by the observer, on luminous clouds, 

 falling stars, and any other phenomena which he may deem interesting, for the 

 notice of which columns 6, 7, and 8 are intended. 



2. If an arch be observed, state if it appear like a simple luminous ring across 

 the sky, or a ring divided transversely into cross ribs, or a mass of light sur- 

 mounting a dark circular segment. These phenomena are not to be confounded. 

 Luminous clouds, clouds illuminated at intervals, streamers, or systems of 

 Streamers, may be also observed. 



3. In marking the place of the arch or beam or corona among the stars, a 

 globe or planisphere, set to the day and hour, will be found very convenient. 

 Three well-determined distant points in the course of an arch or beam (for instance, 

 the point of greatest altitude and its two extremities), will give its position. 

 The breadth of the arch or beam may be estimated by the angular distance of 

 neighbouring stars. If an arch or beam drifts, advantage may be taken of ob- 

 serving wlipn the arch appears exactly between two known stars. The motion of 

 arches and beams is often very apparent and capable of actual measure. Arches 

 often appear to move southwards ; more rarely turn on an axis which approaches 

 to the vertical. 



