§86 SURVEY OF THE COAST 



8. At such suspension, the last microscope stand and the- 

 bar last layeil off' with its microscope stands adjusted, must 

 remain in their places till the work is resumed. The whole 

 must be covered with a tent, and well secured. 



(A tent made for this purpose, with others made for the 

 microscope stands, was delivered with the apparatus.) 



9. Notwithstanding all these precautions, it will be proper 

 to keep a constant watch over the apparatus when left out. 

 and even perhaps to make a fence round it, if it be in a 

 place where cattle pasture. 



10. In the morning, or whenever the work is resumed, 

 every thing must be carefully verified and noticed in the 

 journal. 



11. It is of course understood that the dates before and 

 after noon, the slate of the weather, the temperature of the ex- 

 terior air at stated intervals, and any circumstances that may 

 increase or diminish the confidence in the work at any time, 

 must be inserted in the journal, and that it should contain a 

 detailed account of the manipulation adopted, the persons 

 employed, ^c. 



13. If the base should not finish v.?ith a full length of bar, 

 as is generally the case, the last point determined by the bars 

 should be carefully marked on the ground, and the comple- 

 mentary distance measured by means of a beam compass, 

 or by any other means that shall lead to satisfactory re- 

 sults. 



13. The measurement of a base line should be continued 

 with as few interruptions as possible. Considerable trouble 

 will then be saved in respect to covering, fencing, ^c. the 

 apparatus, and all sudden and unequal changes of tempera- 

 ture in the bars will be completely guarded against. I would 

 therefore advise the operator to finish each day's measure- 

 ment without interruption, and when this cannot be done, to 

 suspend the work till a more favourable opportunity presents 

 itself. 



