Ixiv Introduction to the Makerstoun Observations, 1843. 



« 



The columns are the same as in the daily meteorological observations, except- 

 ing that the columns for the maximum and minimum thermometers are awanting. 

 Abstract of Results, pages 219 — 305. 



111. These Tables have appended or prefixed to them all requisite explana- 

 tions, together with remarks on the conclusions deduced. It may be mentioned 

 here, also, that in the Tables of Abstracts for the Magnetical Observations, summer 

 consists of the months of May, June, and July, while, in the Tables of Abstracts 

 for the Meteorological Observations, summer consists of the months of June, July, 

 and August. 



Ourves of the Term^Day Observations after page 306. 



112. The term-day observations have been projected and printed by a new 

 process, which, as it may be of use in other cases, it may be desirable to describe 

 here. Having obtained a sufficient number of lithographed copies of the curve paper, 

 the observations were projected with the greatest accuracy, and the lines drawn with 

 lithographic ink, by Mr Welsh ; from these drawings the copies in this volume 

 were obtained by the Anastatic process. The advantages of this method are, 1st, the 

 accuracy with which the observations are at once projected from the original obser- 

 vations (instead of being copies merely) ; 2d, that the curve paper has only to be 

 drawn once for all the curves ; Sd, that the expense is considerably less. The curve 

 paper was prepared, and the curves were transfeiTed by Mr R. Appel, lithographic 

 and anastatic printer, Ipswich. 



General Remarks. 



113. It is perhaps desirable that some reasons should be given for the methods 

 of reducing and printing the magnetical observations adopted in this volume. 



114. The westerly declination has been given in the common units, degrees, 

 and minutes, because the units are common ; as it is as easy to give the variations 

 of declination, with reference to the astronomical as to any other meridian, the 

 printed observations are all absolute. They are thus at once comparable with all 

 other observations which have been, or may be, reduced to the common units. 



115. The bifilar and balance magnetometer readings are given in scale and 

 micrometer divisions respectively, because no common unit of force has been yet 

 agreed on, and because, in the case of the balance magnetometer, I had every reason 

 to believe that an accurate value of the micrometer divisions had not been obtained. 

 The results have been converted into parts of force, because it was necessary for con- 

 clusions on the variations of the total force and of the dip. If, however, the unit at 

 different places must be variable, it seems desirable that it should be the same at 

 the same place for the horizontal and vertical components and for the total force. 



