66 



Anniversary Meeting. 



[Nov. 30, 



equator, showing the extinction of the mean movement near the 

 equinox. His researches on the lunar-diurnal variation of magnetic 

 declination are of very great interest. Besides being an independent 

 discoverer of the existence of this variation, he showed that near the 

 equator its law in December was the opposite of that in June. He 

 found, too, that the lunar-diurnal variation was in December some- 

 times greater than the solar-diurnal variation — that the lunar action 

 was reversed at sunrise, and that ft was much greater during the day 

 than during the night, whether the moon was above or below the 

 horizon. Finally, he found that the lunar- diurnal law changed (like 

 the solar-diumal law at the equator) near the equinoxes, so that, as a 

 consequence, the laws for the southern and northern hemispheres 

 were of opposite natures. 



Another and very remarkable fact discovered by Mr. Broun was 

 that the variations from day to day of the earth's daily mean 

 horizontal force were nearly the same all the world over. He found 

 certain oscillations in these daily means which were due to the moon's 

 revolution, and others having a period of twenty-six days ; the latter 

 he considered as due to the sun's rotation. It results from these in- 

 vestigations that the observed variations of the earth's daily mean 

 horizontal force have been represented with considerable accuracy in 

 all their more marked features, by the combination of the means 

 calculated for these different solar and lunar periods. During the 

 discussion of these periods, Mr. Broun found that the great magnetic 

 disturbances were apparently due to actions proceeding from par- 

 ticular points or meridians of the sun — a fact this (if verified) of 

 very great importance. 



In meteorology he has shown the apparent simultaneity of the 

 changes of daily mean barometric pressure over a great part of the 

 globe, and he has likewise discovered a barometric period of twenty- 

 six days nearly. He was also the first to commence and carry out, 

 during several years, a systematic series of observations of the motions 

 of clouds at different heights in the atmosphere ; and, lastly, he has 

 found certain laws connecting the motions of the atmosphere, and the 

 directions of the lines of equal barometric pressure. 



A Royal Medal has been awarded to Dr. Albert Giinther, F.R.S,, 

 for his numerous and valuable contributions to the zoology and 

 anatomy of fishes and reptiles. 



Dr. Giinther's labours as a systematist and a descriptive zoologist 

 have been devoted chiefly to the order of Fishes, Reptiles, and Am- 

 phibia. Upon these he has published during the last quarter of a 

 century a very long series of valuable papers, whereby our knowledge 

 of the structure, affinities, and distribution of the genera and species of 

 those interesting groups has been greatly advanced. We owe to his 

 indefatigable exertions the excellent condition in point of arrangement 



