63 



147. On steamboats or railroads the barometer, if hung up in any 

 manner, should be secured against striking or pounding the side of 

 the room or car. In wheeled vehicles the barpmeter should l)e car- 

 ried by hand, supported by a strap over the shoulder, or held upright 

 between the legs. It should not be allowed to rest on the floor, as a 

 severe jolt may break the tube. On stage routes, when impracti- 

 cable to carry it by hand, hang the barometer on a hook inside the 

 stage and securely fasten the lower end, so that it will not swing 

 when being thus transported. If carried on horseback, it should be 

 strapped over the shoulders of the rider, where it is not likely to be 

 injured. 



148. Change of location. — It sometimes becomes necessary to 

 change the location of instruments from one office room to another or 

 to a different point in the same room and making little or no change 

 of elevation. In such cases the barometer box can be moved bodily 

 with the instruments in place. The first step is to prepare the wall 

 at the new location by setting up the necessary wood strips and the 

 screw at the top on which the hook of the barometer box can be 

 hung. If no change is to be made in the elevation this screw must 

 be at exactly the same height as the corresponding screw at the old 

 location. After the usual comparative readings have been made 

 and all is prepared the barometer cisterns will be screwed up until 

 full of mercury and the box moved bodily in an upright position and 

 secured at the new location. Comparative readings should not be 

 made after the removal until an interval of two or three hours has 

 elapsed, unless the temperature is practically the same in the two 

 locations. 



149. Shipment of serviceable hon^oiiieters. — Every possible care is 

 taken at the central office to secure the highest attainable precision 

 in the pressure observations at stations and to ascertain the amount of 

 abnormal errors that sometimes develop in the use of instruments. 

 To this end defective instruments are called into the central office 

 for recomparison, and obviously it is of the highest importance that 

 every precaution be taken in packing such instruments to insure 

 their safe arrival at destination. 



150. In reporting on defective or unserviceable barometers, observ- 

 ers should state clearly the condition of the instrument, and whether 

 or not the mercury can be screwed up to such an extent as to permit 

 of forwarding the instrument "mercury filled." Such barometers 

 are called in by the official in charge, division of supplies, central 

 office, by exp7'ess.^ and observers should keep on hand constanth^ a 

 small supply of the special "' Notice," " Glass," and " Very fragile " 

 labels, two or three of which should be tacked or pasted on outside 

 cover of box in a conspicuous manner. 



151. Shipment of empty instruments. — ^When barometers are so 

 seriously defective that check comparisons can not be made or are 

 valueless, observers will be authorized to forward the barometer to 

 Washington, first carefully emptying all the mercury, which will be 

 preserved in a clean bottle and packed in the box with the barometer. 



(B) CARE AND USE OF BAROGRAPHS 



152. Exposure of barographs. — The general principles of the expo- 

 sure of barometers given in paragraph 89 apply to barographs also. 



