384 I'HILOSOI'HICAL TUANSACTIONS. [aNNO 1730. 



is in common to the four following, and serves to show how many times its 

 weight any loadstone sustains. 



The author also explains the use of these tables, by instances under each 

 denomination. 



An Account of a Book entilled, Jo. Frider. JViedleri* Observationes Meteoro- 

 logicce et Astronomiae, Annorum \ 7 IS and \Tig, &c. IVittembergce, Anno 

 1729. N°412, p. 250. 



The author, after dedicating his Tracts to the Royal Society, gives a de- 

 scription of the particular sort of barometer, thermometer, hygrometer, and 

 hyetometer, which he made use of in the subsequent observations. This book 

 gives a diary of the weather, from the vernal equinox of the year 1728, to 

 that of the year 1729; containing the daily state of the barometer, thermo- 

 meter, wind and weather, with the quantity of rain during that time. To 

 this the author annexes some select meteorological and astronomical observa- 

 tions, which he describes at large. 



The first he takes notice of is a remarkable halo round the moon, on 

 Feb. 20, 1728, at 7^ 45"" in the evening, when the moon was not far distant 

 from the meridian, and about her first quarter. The diameter of the halo 

 occupied about 47 degrees. Its arch was 4^- deg. broad. Within it was red, 

 and towards the extremity pale; exhibiting entire a beautiful spectacle for 

 about 4 minutes. The same day at noon, he observed 13 spots on the sun; 

 the largest equalling -jL- of the sun's diameter; and the spirit fell to go deg, of 

 the English thermometer. 



April 4, 1728, he observed an aurora borealis. 



June 20, another, which is described in the Act. Erudit. Lips. Ann. 1728, 

 p. 373. 



Oct. 7, a very remarkable one appeared in the n. e. A white arch, extend- 

 ing between the w. and n. e. quickly assumed a black colour, and then divided 

 into three other concentrical arches equally black. From these some radia- 

 tions arose as usual, but shorter, A little afterwards these likewise ceased, and 



• John Fred. Weidler was professor of Mathematics at Wittemberg. Besides a number of com- 

 munications to the Royal Society, contained in volumes 36, 38, 39, 4-0, 41 of the Philos. Trans. 

 he was author of several separate works : as, 



1. Institutiones Mathematicae, in 8vo. 1725. This is a very thick volume, and contains a general, 

 tliough concise course, of all the mathematical sciences. 



2. Observationes Meteorologicae et Astronomicae, 1720, above described. 



3. Historia Astronomica, in 4to. 1741- 



