156 



Davis' Patent Solar Attachment. 



This invention is destined to supersede all other solar attachments, being by far 

 the most accurate, the most simple, and the cheapest in use. The sun observations are 

 made with the instrument's telescope direct, whereby greater range and power are 

 secured, and limiting the adjustments to those common to the instrument proper 

 itself. It can be attached to any engineers' and surveyors' transit which has a good 

 vertical arc or full vertical circle. A great many have been placed on our transits 

 (sizes Nos. 1, 2, 3 and occasionally on No. 4), for the use of U. S. Deputy Survey- 

 ors, and others having occasion to do solar work. 



However, as its manipulation involves a few mathematical calculations, differing 

 somewhat from ordinary solar attachments, we advise our patrons to carefully read 

 pages 73 and 75, etc., of manual, where a full description will be found. 



The screen, shown in Fig. 2, can be applied with erecting and inverting tele- 

 scopes. In making an observation with an erecting telescope the full aperture of 

 the object glass is utilized, but with an inverting telescope it must be limited 

 to about X or ^ inch diameter to get the wires sharply defined on the screen. To 

 this end the telescope cap is provided with a central opening, permitting of such an 

 adjustment, which may be closed entirely when not in use. 



Attachments shown in Figs. 3 and 4 are for direct observation when the sun's 

 altitude does not require the screen. These latter attachments are now made by us 

 in a manner superior to those shown in these cuts on opposite page. They are 

 mounted as in Fig. 5, upon a frame, readily attachable to the eye-piece by means of 

 a clamp, which can be clamped in any position most convenient for the observer. 

 To bring the colored glasses or the prism before the peep-hole of the eye-piec<>, it is 

 only necessary to revolve them, hence they can be used in rapid succession. It will 

 be seen that these solar attachments are easy to manipulate, and therefore must 

 insure better results than heretofore obtainable with mechanical devices of any 

 other kind. 

 Price of Solar Screen as in Figs. 1 and 2, $6.00 



" Prism and Colored Glasses, see Figs. 3 and 4, but of improved 



mounting, as in Fig. 5, 12.00 



" Solar Screen with prism and colored glasses combined, . . 18.00 



If we attach the screen to instruments which are sent to us for that purpose, we 

 must make an extra charge of $4.00. In such cases the telescope should be sent to 

 us. 



C. L. JJerger & Sons' Patent Inclined Square. 



For Sun Observations with Davis' Patent Solar Attachment. 



This device consists of four additional wires forming an inclined square of equal sides placed at an angle of 

 45 with the usual cross wires, and equi-distant from the latter's point of intersection in tin- Survivor's Transit 

 Telescope. The space contained within this square, as will be seen in the greatly enlarged Figures g and j?a, is 

 slightly 'smaller than the sun's disc; thus an observation of the sun for position can be made by simply setting 

 the telescope by means of the tangentscrews until the four segments, formed by the bl.ick lines against tl. 

 disc of the sun, are of equal size. In this manner the sun's disc can be better hisectftl, ;is wl^-ii it must be 

 quartered by the cross lines alone but, if desired, both methods can be applied as a check upon each other. 



The arrangement of the wires in the inclined square; is in no way confusing, as it keeps the cross and stadia 

 wires distinctly apart for the regular work of the transit, and, in rapid work, is a help to distinguish the 

 horizontal from the stadia wires, as shown above, which cannot be said of the erect square H also patented, 

 shown on the page illustrating the various sighting wire diaphragms. Part I. 



I'rice of Patent Inclined Square, but only, >///// <>r<Ifr?d with the instrument, extra . W4.OO 



also provided with Stadia Wires, as in cut, 7.<i<) 



" with cross and stadia wires for instruments of other make 1O.OO 



