IS 



Care of Instruments.* 



Do not allow the legs of your tripod to play loose on the tripod head ; keep nuts 

 and bolts always well tightened up against the wood. Examine the shoes from time 

 to time, and sharpen them if necessary, also screw the shoes tight, if wear and tear 

 loosen them. Be sure your instrument is well secured to its tripod before using it. 

 Bring all four levelling screws to a seat before shouldering instrument. Let the needle 

 down upon its pivot as gently as possible, and allow it to play only when in use ; if too 

 far out from its course, check movements of needle carefully by means of lifter. 

 Never permit playing with the needle, especially not with knives, keys, etc. Be sure 

 to arrest the needle after use, and screw it well up against the glass cover before 

 shouldering the instrument. 



As a rule the compass needle is balanced as nearly as possible for the 

 latitude in which an. instrument is to be used. If only a trifle out do not meddle, 

 inasmuch as one can do more harm to the pivot than a small error from non-balancing 

 would amount to, l>ut if the compass needle requires to be rebalanced 

 proceed as follows: 



Kemove the compass glass which is held down by a circular ring on top of the 

 glass, which may be removed by inserting the blade of a knife where the two ends of 

 this ring come together and prying gently upward. By means of a piece of beeswax 

 slightly softened, the compass glass may be readily lifted. Then raise the needle up 

 its entire length by means of the lifter and carefully remove it with a pair of tweezers. 

 When the needle is balanced it should be as carefully placed back with the lifter up 

 as before to retain the sharpness of the pivot. If the compass glass needs to be re- 

 moved entirely, unfasten the two screws that screw the stud for the telescope tangent 

 screw to the standards. Don't remove the telescope from its wyes. 



Do not clean the glass cover or the lenses with a silk handkerchief ; breathe over 

 the compass-glass and reading lens if one is used, after cleaning. Examine the but- 

 tons of your coat with regard to iron that may be concealed in them, also beware of 

 nickel-plated watch chains, etc. To clean the object-glass and the lenses use a fine 

 camel-hair brush. If dust or sticky or fatty matter cannot be removed with the 

 brush, take an old clean piece of soft linen, and carefully wipe it off. Do not unscrew 

 the object-glass unnecessarily. this is apt to disturb the adjustment of line of colli- 

 mation. The lens nearest the eye of eye-piece, as well as the front side of the object- 

 glass, need careful brushing with^ne brush from time to time. 



If dust settles on cross-hairs and becomes troublesome, unscrew the eye-piece and 

 object-glass, and gently blow through the telescope tube, cover up both ends and wait 

 a few minutes before inserting the eye-piece and object-glass. Be sure to have the 

 object-glass cell screwed well up against its shoulder, and then examine the adjustment 

 of line of collimation (see adjustment of line of collimation). Do not grease the ob- 

 ject-slide of telescope, or screws that are exposed to dust ; use a stiff tooth-brush to 

 clean slides or threads if dusty. 



To take out the eye-piece, unscrew the screw at the end of the main tube, take 

 hold of the eye-piece and pull it out. 



To focus the cross-hairs, take hold of the eye-piece cap and turn it in a screw-like 

 manner until cross-hairs appear distinct, and as if fastened on the object when the 

 head is being moved. 



Should there ba any fretting in the telescope slide, take it out, and endeavor to 

 smooth the rough part with the back of a pocket knife. 



If the focussing' slide seems to work too hard, everything else being right, :'t 

 is generally caused by the lubricant on the pinion hardening in cold weather, and the 

 same cause may also make the focussing slide work too freely in hot weather by soften- 

 ing, i. e., when not staying in place when in a vertical position. If the slide moves 

 too freely it should be tightened by running out the slide to its full length, then apply- 

 ing a screw-driver to the screw on top of the focussing screw and turning a very small 

 part of. a turn until the required friction is obtained. If the slide works too tightly 

 run in the slide, unscrew the top screw one turn, gently tap it by the screw-driver 

 handle to release it, and then tighten to the required stiffness. 



To prevent the focussing slide from fretting, usually due to the inrush of air car- 

 rying dust and grit when slide is being run out causing momentarily a rarefied space, 

 wrap a piece of chamois skin over the barrel in shape of tubular form and fasten by 

 means of rubber bands or sewing. In an emergency fine watch-oil may be used to 

 grease the slide should it continue to fret, until the instrument can be sent to the 

 maker. In case of rain during non-use, place the telescope vertical, object end up, 

 and no water can enter the telescope. 



Xever use emery in any form about any part of a Transit or 

 a Level, whether tangent screws, slides or centers. If anything must be used, a very 

 little powdered pumice-stone mixed with fine watch-oil is all that is advisable, and 

 after grinding, then clean thoroughly. The uninitiated are advised to do no grinding 



* For additional suggestions see p. 14. 



