NOTES AND MEMORANDA. 45 



the position which the latitude requires by a screw, which presses 

 upon an arm marked with the degrees of latitude from 0° to 70°. 



In order to adjust the instrument, it is placed on a perfectly hori- 

 zontal sui'face ; the mirror having been removed, a metallic rule 

 ("forming a diameter of the dial plate) is fixed, so as to slide easily on 

 the axis of the movement, which traverses it like a spindle. This 

 rule is terminated at its extremities by two perpendicular pieces, the 

 shorter one being pierced with a small hole, the other marked with 

 a division representing the equation of time and the declination of the 

 sun for every ten days, connected by a continuous line. At the base 

 of the shorter upright the rule has an aperture, through which can 

 be seen the figures on the dial. To set the apparatus to the hour, 

 the rule is turned round the axis like the hand of a watch until the 

 exact hour and fraction of the hour at which the observation is made 

 are seen in the aperture, and the division which represents it on the 

 dial coincides with an index placed at the edge of the aperture. 



For final adjustment it is only necessary to turn the instru- 

 ment horizontally on the table, inclining it more or less on its sujj- 

 port, until a ray of the sun, passing through the hole of the short 

 upright, produces on the line of declinations placed on the opposite 

 one, a small image of the sun which falls exactly on the point corre- 

 sponding to the day of the year. This operation takes only a few 

 moments, and is extremely easy. 



This done, the instrument is adjusted ; the screw on the circle of 

 latitudes is tightened, the rule taken away, and the stem of the mirror 

 is slid into the axis of the movement. The mirror can be turned in- 

 dependently, by which means the reflected ray may be directed to any 

 azimuth. A fixed horizontal ray is thus obtained, which may be further 

 reflected to another plane mirror, placed at some distance and movable 

 on a pedestal, so that the ray may be directed wherever it is wanted. 



When the exact time is not known, the instrument may still be 

 adjusted in a way which is apj^roximately correct, by adjusting it at 

 about noon. It may also be adjusted first at about 9 a.m., and then 

 about 3 P.M. Each time this is done a line is drawn on the table 

 with a pencil, the foot of the instrument serving as a rule. These 

 two lines form an angle which is bisected, and along the line which 

 bisects it the foot of the instrument is placed. The latter is in this 

 way adjusted for midday. 



The clock movement has an anchor scapement, and could move a 

 much larger mirror. A small dial placed on the drum and divided 

 into sixty minutes, on which a minute-hand moves, allows the regu- 

 larity of the motion to be verified. The dial of hours and the division 

 for the days are enamelled, and consequently proof against weather. 

 The whole apparatus is very portable. 



New (Auditory) Sense-organs in Insects. — Professor Graber, of 

 Czernowitz, announces * the important discovery of organs, probably 

 of an auditory nature, which he has foimd, one in the antennae of 

 adult Diptera, the other in a larva of a species of the same order. 



1. Oioci/st-like Organ in the Antennce of Diptera (Plate IV. Figs. 1 

 la, and lb). — This was observed in Syrphiis balteatus. The structure 

 * ' Arrhiv f. Mik. Aimt.,' vol. xvi. p. oG. 



