OF THi: TNITEI) STATES. a85 



1. It is necessary to mark in tlic preliniinat v measiirc- 

 meiit and the alignment ot the hasc a nunibti ol points, at 

 equal and moderate distances I'rom each otiier, so t:iat at 

 least one ol these points may be found in each day's work of 

 the accurate mcasuri-nicnt. lor the purpose of showing whe- 

 thci' the lcn2;th of a l)ar had heen omitted, or written twice. 



2. The jomnal must have re2;ular columns for the obser- 

 vations made at the laying; oft" of each box. and a c(tlumii 

 should !)c left for incidental remarks, ihe liist eolninn sliow- 

 ing t!ie number of each barliomthe l)e^inninii; to the end. 



3. I he time at which the adjustment of each bar is effect- 

 ed by the microscopic apparatus sliould be noted to the near- 

 est minute. Tliis may be entered in the second cohnnn. It 

 is evident that tliis will serve to check the registerinu; of the 

 bars, by showinn; whether any mistake had been made that 

 was not accounted for in the remarks inserted in the left co- 

 lumn. 



4. The stand of the sector, indicating the position of the 

 bar towards the horizon, toj^eilier with the stands of the se- 

 veral thermometers, marked and placed after each other in 

 the order in which they have been read, should occupy the 

 third or next column. 



5. The points of coincidence of each of the marks stated 

 in Art. l with the bar or any fraction of it must be carefully 

 marked in the next column. Likewise the passage of any 

 ditch, fence, or other permanent object that may be of use 

 in fmding any particular point in the line after having pass- 

 ed it. 



6. At every fifty or hundred bars, a mark should be left 

 behind, so accurately determined, that, in case of accident, 

 the measurement n»ight be auain made from it, without the 

 necessity of returning to the bei!;iruiing. These marks should 

 be numl)ered. and the time of ()lacing them should be writ- 

 ten in the journal. 



7. In the evenimr. or at any other time when the work is 

 susjjeiidrd, tlie place of the last microscope apparatus taken 

 oft' should be maikedand registered in the journal. 



vol.. II. — e i 



