152 REPORT — 1844. 



Lamont justly remarks, is affected with undulations which can hardly be re- 

 ferred to the direct action of the solar heat. The course of the mean decli- 

 nations exhibits a continual and tolerably though not quite uniform decrease 

 of about 7' per annum, but without any indication of regular periodical fluc- 

 tuation, either annual or otherwise. 



The 'Annales de Cliemie' (vol.x. 3rd series) also contains a similar summary, 

 not accompanied however by graphical projections, by M. Aime, of the re- 

 sults of nineteen months' consecutive magnetic observations made by him at 

 Algiers, from June IS^-l to Dec. IS^S inclusive. These exhibit, as respects 

 the declination, only one diurnal minimum, varying in epoch with the season 

 from 7*^ to 8^ 30'" a.m., and a single maximum varying also in epoch, but 

 contrarywise with the season, from 2^ p.m. to noon. The fluctuation is 

 nearly double in summer as comnared with its amount in winter. The cor- 

 respondence of the march of this element with the temperature has appeared 

 to M. Aime so exact, that he suggests the observation of it continuously on 

 the occasion of solar eclipses as an object of especial interest. 



The present change of declination at Algiers appears to be about 24-'> 

 decreasing. By some observations reported by M. Aime as having been 

 made in 1832 and 1833 by Captain Berard, the needle may be presumed to 

 have attained its maximum westerly declination about that epoch. The in- 

 clination diminishes at Algiers at the rate of about 6' annually. 



Meteorological Department. — Discussio7i of Meteorological Observations. 



At the last meeting of the British Association, Sir J. Herschel, acting as a 

 committee for the reduction and discussion of the meteorological term obser- 

 vations for 1835-38, reported among other matter, that by the aid of these 

 observations it had proved practicable, in specified instances, to trace the 

 progress and to assign the magnitude, direction and velocity of atmospheric 

 movements in the nature of waves over nearly the whole of Europe, and that 

 in a manner which, if pursued further, could hardly fail to afford real and 

 valuable additions to meteorological science. Being obliged however, from 

 the pressure of other occupations, to leave the inquiry at this point, Mr. Birt 

 volunteered to continue it under the auspices of the Association, and was 

 accordingly added to this committee for that purpose. The progress made 

 by him in it will be appended in his own words, as part of this report, accom- 

 panied with a letter explanatory of his views on the subject, and with models 

 of certain atmospheric waves in several successive states of their progress 

 over Europe, which will be submitted to the Physical Section for their in- 

 spection. [See Mr. Birt's Report in this Volume.] 



In the discussion of meteorological observations, the most serious obstacle, 

 and that of the most formidable and repulsive character, is the enormous mass 

 of calculation (necessitating transcriptions, &c.) required for their adequate 

 reduction and preparation for the uses of the theorist ; while, on the other 

 hand, the method of inductive inquiry, which seems most applicable to the 

 subject in its present state (the " Method of Curves," as it has been termed 

 by an eminent writer on inductive science), I'equires the observations, when 

 reduced, to be in a great variety of cases projected on paper in the form of 

 diurnal, monthly or annual curves. On the other hand, such is now the per- 

 fection of every description of mechanical workmanship, and such the profu- 

 sion in which the talent of mechanical contrivance is actually found to be 

 disseminated among practical and theoretical persons in every class of life 

 and in everj' line of human research or business, that the time is clearly ar- 

 rived when arrangements of mechanism may be safely relied on to supersede 



