On the Lunar-diurnal Variation of the Magnetic Declination. 479 



under the circumstances under which I have worked, the two sub- 

 stances do not combine. 



The product of the reaction of oxalate of ethyle upon the mixture 

 of the ethyle-bases, when distilled in the water-bath, yields triethyl- 

 amine free from ethylamine and diethylamine. 



The residue in the retort solidifies on cooling into a fibrous mass 

 of crystals of diethyloxamide, which are soaked with an oily liquid. 

 They are drained from the oil and recrystallized from boiling water. 

 Distilled with potassa, these crystals furnish ethylamine free from 

 diethylamine and triethylamine. 



\ The oily liquid is cooled to 0°, when a few more of the crystals 

 are deposited ; it is then submitted to distillation. The boiling-point 

 rapidly rises to 260°. What distils at that temperature is pure 

 diethyl-oxamate of ethyle, from which, by distillation with potassa, 

 diethylamine free from ethylamine and triethylamine may be 

 obtained. 



January 10, 1 86 l.r— Major-General Sabine, R. A., Treasurer and Vice- 

 President, in the Chair. 



The following communication was read : — 



" On the Lunar-diurnal Variation of the Magnetic Declination ob- 

 tained from the Kew Photograms* in the years 1858, 1859, and 

 1860." By Major- General Edward Sabine, R. A., Treas andV.P.R.S.f 



Having communicated to the Royal Society in a recent paper an 

 analysis of the disturbances of the declination in the years 1858 and 

 1859, shown by the photograms of the Kew Observatory, I propose 

 in the present paper to submit the results of the lunar-diurnal 

 variation of the declination in the years 1858, 1859, and 1860, 

 obtained from the same source. - The directions of the declination 

 magnet at the instant of the commencement of every solar-hour 

 having been tabulated from the photograms, and the final normals 

 for each month and hour computed, after the omission from the 

 record of all the hourly directions which deviated 3'* 3 from their 

 final normals, — the differences were taken between each of the re- 

 maining hourly directions and the final normal of the same month 

 and hour, and were entered afresh in lunar monthly tables, having 

 the lunar days in successive horizontal lines, and the twenty-four 

 lunar hours in vertical columns, each difference being placed under 

 the lunar hour to which it most nearly approximated. The entries 

 in these tables should consequently represent directly the lunar in- 

 fluence at the different lunar hours, subject only to minor disturb- 



* The term Photogram is adopted in place of Photograph in conformity with 

 modern usage. 



t [Note added on February 8th, 1861.] When this communication was read to 

 the Royal Society on January 10th, 1861, it contained the lunar-diurnal variation 

 for the years 1858 and 1859 only : whilst it was passing through the press, the 

 calculation of the lunar-diurnal variation for 1860 was completed, aud the results 

 in that year have been added. 



