] 38 Instructions Jor Making mid Registering 



rise to that remarkable alternation of south-east and north-west 

 winds, which forms so distinguishing a feature of our climate — 

 or consider it, secondly, as the farthest extremity of one of the 

 two great lobes of land which form the terrestrial part of our 

 globe, and as such, constituting at once a barrier to the currents 

 and tides of two great oceans, and a limit to their climates — or, 

 lastly, as a great nautical station, and one not devoid of diffi- 

 culty and danger, in which every consideration of practical inte- 

 rest combines to stimulate the curiosity of the theorist, and give 

 importance to the results of his inquiries. 



As these pages may fall into the hands of many who have 

 been little in the habit of observing systematically, or who may 

 not be in possession of instruments of the nicest construction, at- 

 tention to the following instructions is recommended as the means 

 of rendering their observations most available for useful purposes, 

 and comparable with each other, and, with those intended to be 

 refered to as standards. 



I. General Recommendations and Precautions. 



1. The continuity of observations ought io be interrupted as little as pos- 

 sible hy changes in the adjustments of instruments — in their places — expo- 

 sure — mode of fixing— or of reading off and registering them. Whenever 

 any alteration in these or any other particulars takes place, especially such as 

 are likely to affect the zero points, or otherwise to influence the mean re- 

 sults, it should be noticed in the register. 



2. So far as possible, registers should be complete — but if by unavoidable 

 circumstances of absence, or from other causes, blanks occur, no attempt to 

 fill them up by general recollection, or by the apparent course of the numbers 

 before and after, should ever be made. 



3. The observations should, if possible, all be made by one person — but as 

 this may often be impracticable, the prmcipal observer should take care to 

 instruct one or more of his family how to do it, and should satisfy himself b}-" 

 many trials that they observe alike. 



4. The entries in the register should be made at the time of observation, 

 and the numbers entered should be those actually read off on the respective 

 scales of each instrument, on no account applying to them previous to entry 

 any sort of correction, as for instance for zero, for temperature, capillarity, ^c. 

 All these and the like corrections, being matter of calculation and reasoning 

 from other observations, are to be reserved till the final discussion of the se- 

 ries, and for separate determination and statement.* 



5. If copies be taken of the registers, they should be carefully compared 

 with the originals by two persons, one reading aloud from the original and 



• We regard this as of the liighe^t importance. 



