EECEEATIVE SCIEJ^'CE. 



167 



time and to the given declination ; and having 

 verified all the steps of the process, he looks 

 through the telescope with the certainty that 

 the object — the comet, star, or planet, etc. — is 

 in the field of view, whether visible or not. 



With a telescope such as the one last re- 

 ferred to, it is not likely that a comet will be 

 visible in the day-time ; but Venus, Jupiter, 

 or stars of the first magnitude, can be seen 

 in broad day-light, if the sky be clear. They 

 wUl often appear exceedingly faint ; but there 

 they are, their apparent places in the heavens 

 having been found by the circles attached to 

 the instrument, and not by sweeping the 

 heavens. 



The instrument which it is the special 

 object of this paper to describe, was con- 

 structed by the writer for his own amuse- 

 ment ; and a great number of trials have 

 proved that its design, that of insuring the 

 presence of the celestial object somewhere in 

 the field of view, can always be accomplished. 



Let not astronomers smile at the rough- 

 ness of the instrument, till they are told that 

 the graduated circles by which the instru- 

 ment is directed to an object are not so much 

 as one inch in diameter, and that the divisions 

 were cut in brass by the hand of an amateur. 



The history of the instrument is as fol- 

 lows : — In the year 1850, a friend of the 

 writer was amusing himself in constructing 

 an equatoreal mounting for a two-inch re- 

 ■ fractor, according to a design of his own. 

 He was a good mechanic ; but having chosen 

 wood (which he thought would do for this 

 rough purpose) as the material upon which 

 to fix his graduated circles, carefully executed 

 on paper, he met with an unsatisfactory re- 

 sult, which the writer predicted woiJd be the 

 case. It occurred to the latter to attempt to 

 divide the brass circles on a " clip," used for 

 attaching the telescope to a post, or other- 

 wise, by means of a screw connected with it, 

 the " clip " having the two motions already 

 referred to. The graduation was a work of 

 considerable laboiir ; but, besides the advan- 



tage of making use of an article already pos- 

 sessed, the plan had several advantages con- 

 nected with the smallness of the diameter of 

 the circles, to be set against the disadvan- 

 tages. The result was very satisfactory. The 

 graduations were tested by the sextant, and 

 were found to be sufficiently good. 



Amateur astronomers will enter into the 

 feeling of boyish delight with which the 

 first fijpding of Yenus in the broad day with 

 the instrument was associated. The writer 

 would have been amply rewarded for his 

 pains, if the pleasure which the exhibition 

 and explanation of the little instrument has 

 given him since the time referred to were 

 his sole reward. 



Among those to whom he has shown it, 

 and who have expressed themselves as highly 

 pleased with the instrument, the writer is 

 proud to refer to a lady whose interest in 

 astronomy, and whose powers of exciting an 

 interest in the study of this glorious science 

 in others, have lately been so pleasantly ex- 

 emplified in the little gem called " Telescope 

 Teachings." 



"William C. Bubdeb. 



Observatory, Clifton, Bristol. 



STEEEOSCOPIC PHENOMENON. 



I WAS amusing myself one evening with a 

 stereoscope, and, having exhausted my stock 

 of stereoscopic pictures, I placed in the in- 

 strument a small photographic portrait, about 

 three inches by two, and as nearly as pos- 

 sible in the centre, so that one-half was 

 visible to one eye, and the other half to the 

 other eye, and was surprised to find on look- 

 ing at the picture, with both eyes open, that 

 that side which could only be seen by the 

 right eye appeared to be seen by the left, and 

 that seen by the left eye appeared to be seen 

 by the right. I submit the case to the con- 

 sideration of stereoscopists, in the hope of 

 obtaining an explanation. Stebeo. 



