The telescope of the transit reverses at both the eye and object ends, and is 

 thorough!}' balanced when focussed for a mean distance. 



The telescope of the wye and dumpy level is also balanced each way from the 

 center of the vertical axis when focussed for mean distance and with the sun-shade 

 attached to it. 



Spirit-Levels. 



The Spirit Levels used in our instruments are carefully ground, filled and tested 

 by us in person. 



Those for the highest class of engineering work are sometimes provided with an 

 air chamber by which the length of the bubble can be regulated according to tem- 

 perature. The levels for astronomical instruments have air chambers, and are filled 

 with ether, but in field instruments ether is not adrnissable, owing to the high 

 degree of expansion and contraction in that fluid with changes of temperature. 

 For these we use a composition fluid that \ve have found to be more sensitive and 

 quick-acting than that used in instruments we have seen of other makers. 



Our astronomical levels are so ground that a depression through one second of 

 arc causes a displacement of the bubble through about Jj of an inch. The curva- 

 ture or sensitiveness of our levels for field instruments we adapt carefully to the 

 instruments and the kind of work to which they are to be applied. With too sen- 

 sitive a level the position of the bubble would be too uneasy to work with, while 

 too low a sensitiveness would not reveal the full qualities of an instrument. Persons 

 ordering instruments of us will confer a favor by stating for what purpose they are 

 intended, whether for water works, for railroads, or for general use, so that we 

 can use our judgment for their benefit. 



Gradienter Screw.* 



[Description to be found, elsewhere ] 



This is attached to the clamp of telescope of all of our transits except the plain 

 transit. This attachment was first introduced by Prof. Stampfer, of the Vienna 

 Polytechnic School. It does not add to the weight of the instrument, and once 

 used we have found it to be universally approved by our customers. By means of 

 it grades can be established, and horizontal distances, vertical angles and differences 

 of level can be measured with great rapidity. Indeed this attachment to an en- 

 gineer's transit is one of the most useful introductions in practical engineering. 

 It is so universal in its application to railroad and general work, that when once 

 used it will afterwards form an indispensible part of an engineer's outflt. 



Fixed Stadia Wires for Distance Measurements. 



We have specially devised an optical and mechanical apparatus for the purpose 

 of placing fixed, or non-adjustable stadia wires so accurately upon the diaphragms 

 of our telescopes that their distance apart will read V : 100' f on any leveling rod, 

 as with the gradienter screw, thus dispensing with a special rod. 



It is well known that adjustable stadia wires are so apt to change their distance 

 apart with every change of temperature, that no reliance can be placed upon them 

 unless previously adjusted. With fixed stadia wires, annoyances of this kind are 

 obviated they are reliable at all times. 



As regards the degree of accuracy attainable by the use of fixed stadia wires, 

 experiments with our powerful telescopes, made optically as perfect as the most 

 advanced optical and mechanical skill enables us, warrant to say that with some 

 experience and proper care the results obtained will approximate and even equal 

 those obtained by chain measurements. The price for this accessory in any new 

 instrument is only $3.00, but if inserted into a telescope sent to us for that purpose, 

 we must charge $10.00. We advise to order both the gradienter screw and the 

 fixed stadia wires, as each in itself, separately or jointly, will prove of great value. 



* Stampfers Gradienter attachment for leveling instruments, as introduced by him in the year 1838 (se 

 Bauernfeind's Vermessungskunde) , is, however, mechanically more complicated as compared with our own, 

 As to simplicity of design and manipulation, we believe, our Gradienter Attachment, as applied to our transits, 

 is unequalled. 



f In all stadia work, the constant, which is the distance from the center of the instrument to a point in front 

 of the object glass equal to its focal length, must be added to every measurement. Thus the constant in our 

 transit No. i, with inyerting telescope, measured from centre of the instrument, is 1.3 feet; same instrument, 

 telescope erecting, 1.15 feet. Transit, size as in No. 2, telescope inverting, 1.15 feet; same instrument, 

 jelescope erecting, 0.94 feet. In our i8-inch Wye level, telescope erecting, this constant is 1.78 feet 



