Intelligence and Miscellaneous Articles. 73 



surface of speculum metal, leveled by a spirit-level ; and when the 

 reflected object could not be seen, attaching to the metal a col- 

 limating telescope, whose optical axis was parallel with the pre- 

 viously leveled surface, and was defined at the focus end by a 

 horizontal slit, illuminated by a lamp at night, so as completely to 

 remove all difficulty of seeing the referring object, and allowing of 

 almost the whole object-glass being brought to bear on the star. 



Difficulty having been found by the students in keeping sight 

 of an object reflected from the artificial horizon, the latter was 

 generally placed on a stand so as to bring it near the eye, and 

 make it thereby offer a large angular space, which was pretty sure 

 not to be exceeded by the shaking of the hand or involuntary 

 movement of the head of an unpractised observer ; but it was 

 found requisite, not only to make the stand firm, but to improve 

 the steadiness of the leveling screws, which was done by making 

 them parts of a fixed frame, with the reflector moveable on them, 

 and capable of being fastened in any position between opposite nuts. 



A sextant with all the improvements (except the opposite read- 

 ings), a full-sized model of a circle, and one of the reflecting 

 horizon, were shown ; but Prof. Smyth did not mean to claim any 

 part of them as his own invention ; for without making any special 

 inquiries as to how far he might have been preceded by any one 

 else, he believed that he had only brought to bear on this subject 

 individual improvements long and well known in other departments 

 of the science ; but as they had never, he thought, been so com- 

 pletely united before, and as such a reunion might enable observa- 

 tions often to be obtained when now they are given up, he hoped 

 that the communication might not be uninteresting to some of the 

 numerous working members of the Society, 



XII. Intelligence and Miscellaneous Articles. 



ON THE PRODUCTION OF INSTANTANEOUS PHOTOGRAPHIC 

 IMAGES. BY H. F. TALBOT, ESQ. 



TT will probably be in the recollection of some of your readers 

 ■*- that in the month of June last a successful experiment was tried at 

 the Royal Institution, in which the photographic image was obtained 

 of a printed paper fastened upon a wheel, the wheel being made to 

 revolve as rapidly as possible during the operation. 



From this experiment the conclusion is inevitable, that it is in our 

 power to obtain the pictures of all moving objects, no matter in how 

 rapid motion they may be, provided we have the means of sufficiently 

 illuminating them with a sudden electric flash. But here we stand 

 in need of the kind assistance of scientific men who may be acquainted 

 with methods of producing electric discharges more powerful than 

 those in ordinary use. What is required, is, vividly to light up a 

 whole apartment with the discharge of a battery : — the photographic 

 art will then do the rest, and depict whatever may be moving across 

 the field of view. 



