434 SCIENTIFIC EXPERIMENTAL APPARATUS. 



3. Portable transit instrument^ by Herbst, of Pulkowa. Aperture of 

 telescope, 2f inches; focal leugth, 33 inches. Eye-piece at eud of axis. 

 Described in Vol. VIII of the Annals of the Observatory, p. 28. 



4. Bowditch comet-seel-er. — Ajierture, 4 inches; focal length, 33 inches. 

 Described in Vol. VIII of the Annals of the Observatory, p. 32. 



5. Telescope J by Lerebours. Aperture, 3 inches ; focal length, 50 

 inches. 



6. Telescope, by Alvan Clark & Sons. Aperture, 3^ inches; focal 

 leugth, 39 inches. Object-glass slightly damaged. 



7. Variation transit, by Trough ton & Simms, of London. Aperture 

 of telescope. If inches ; focal length, 18 inches. 



8. Traveler's transit theodolite, No. 3527, by L. P. Casella. 



9. Sextant, by Spencer, Browning & Eust. 



10. Spectroscope, by Troughton & Simms, of London, with two prisms, 

 and Professor Winlock's apparatus for recording observations, as de- 

 scribed in Vol. VIII of the Annals of the Observatory, p. 33. 



11. Spectroscope, by J. Browning, of London, with one prism, and 

 Professor Winlock's apparatus for recording observations. 



12. Spectroscope, by Alvan Clark & Sons, of Cambridge, witli five 

 prisms and reflecting prism to send the light a second time through them. 

 Dispersive power exceeding that of 22 ordinary prisms. Prisms not 

 movable. Described in Vol. VIII of the Annals of the Observatory, 

 p. 35. 



13. Lens of plate glass. — Focal length, about 40 feet ; aperture, 4 

 inches. 



14. Lens corrected, for chemical rays. — Focal length, 32 feet 5 inches; 

 aperture, 4 inches. 



15. Photometer, by Ausfeld, of Gotha, on plan of Professor Zollner. 

 IG. Occultator (for computation of occultations), on plan of Eev. 



Thomas Hill. 



17. Position circle, read by verniers to minutes of arc. 



18. Thermometric chronometer, by C. Frodsham, of London, ISTo. 3,424, 

 constructed so as to increase its daily rate- by 6.11" on a reduction of one 

 degree Fahrenheit. 



19. Clocl^, by W. Bond & Son, of Boston, No. 312. 



20. Small chronograph, by Herbst, of Pulkowa. 



21. Portions of the magnetic apparatus described in Vol. I, part 1, of 

 the Annals of the Observatory. 



(Property of Professor William A. Rogers.) 



1. Small line and circle graduating engine. This machine is designed 

 for all kinds of graduations, in which the length of the line to be ruled 

 does not exceed 2 inches. The errors of the screw for one-thousandth 

 of an inch have been carefully investigated. It is not automatic in its 

 action, and hence it is not adapted to ruling diffraction gratings. The 

 circular graduations are only aj)proximate. 



