Tangent Screws. 



These are made of Aluminum bronze, or phosphor bronze, and sometimes of ger- 

 man silver, and are provided with strong spiral springs of german silver, which take up 

 afl the dead motion, no matter how long the screw may In- in use, or how worn. 

 They are less liable to get out of order, by blows or accidents, than any of the ex- 

 iging tangent screws, and require little or no attention on the part of the. engineer.. 

 There Is no strain on eit her plate when t lie iust rument is clamped, so that the levels 

 are unaffected. They are set and turned with the (/rratest ease, following themove- 

 neifti Of the finger instantaneously with mathematical precision, and donotacro&A 

 the plate in revolving instrument. We confidently recommend this form ot con- 

 struction to those who have not used our instruments, as the best possible; super- 

 seding the usual methods by means of two opposing screws, or ball tangent screw. 

 great!/ in point of convenience and accuracy, and equalling them in point of steadi- 

 ness. By this construction we are also able to tit our upper and lower circle plates 

 so snugly that it is impossible for dust to enter between them. Our leveling instru- 

 ment < have the clamp and tangent screws so placed that they can be reached by 

 either hand with the same readiness. 



The Compass. 



The Compass circles are graduated to half degrees in quadrants from to 90. 

 The needles are made of superior steel, and tempered all over. A coil of fine wire 

 attached to the end pointing South balances the needle for our latitude, which must 

 le re-balanced if the instrument is used further north or south of this latitude, and 

 must be entirely reversed if used on the southern hemisphere of our earth. At a 

 cost of $10.00 a variation plate can be placed upon our surveyors' transit to set oft 

 the variation of the needle for any particular locality. A stationary pointer just 

 above the graduated ring at the South end, and protected by the glass-cover of the 

 compass, indicates the line joining the vertical plane of the line of collirnaiion of the 

 telescope. By means of a milled-headed nut, also at the South end of compass, 

 serving both as a handle and as a clamp-screw, the graduated ring can be turned 

 past this pointer towards East or West as the case may require. 



Tripod. 



The form we adopt for our instruments is an improvement over what is com- 

 monly termed the 4 split leg " tripod, used extensively in Europe, which unites the 

 yrit,-st strength and steadiness with the least weight. The tripod-head is cast in a 

 single casting, to avoid all small screws, as well as to attain greater stiffness. For 

 the legs we use the best fine grained white ash, taking particular pains that the 

 grain of the wood runs in the direction of the leg. They are still further guarded 

 against all possible accidents by having wooden tongs inserted at their top. When 

 folded, our tripod is better adapted than the ordinary form, for carrying on the 

 shoulder without irritating the place on which it rests. The good qualities of this 

 over the ordinary round leg tripod provided as that is with unyielding brass cheeks 

 to "tighten" the legs, are so great that there is but one opinion regarding its real 

 advantages, and we gladly bear the greater expense incurred in its manufacture. The 

 cast-steel shoes have projections for the foot, to aid in pressing the legs into the 

 ground. Our levels and transits both fit the same tripod, and are of equal length. 



Shifting Tripod. 



We have also adapted to all our engineers' transits the shifting tripod or shifting 



tenter, by which, after an approximate setting of the tripod, the transit can be 



iiateiy brought over a point on the ground. This device we also attach to 



menta with three leveling screws in a most perfect and simple manner, 



and without impairing their steadiness and portability. 



Adjustable Plumb-Bob. 



We ftirnlsh with all our transits a small brass chain and hook, which are 

 connected to the (enters of the instruments. The cord of the plumb-bob can be 

 d or detached from this hook, and by means ot a neat, small and 

 furnished with every Instrument,) the plumb-bob can be ad- 

 justed over the ground at any height, with hardly any effort on the part of the 

 engineer. 



