S'Mgular Pbenbmenon in a Thunder -Clouds 41 



We wanted alfo fmall portable tables, ahd thefe C. Dldot 

 has undertaken. I have begun an edition of Logarithms car- 

 ried to fix decimal places, like thofe given by mylelf and La- 

 caille in 1760, which were publifhed by Marie in 1768, and 

 reprinted four limes afterwards, but Hill with more faults 

 than the firll time. We at length, however, have a perma- 

 nent edition, which it will not be neceflliry to reprint eve:gf. 

 ten years with more errors than thofe before difcovered. 



M. Bogdanich, afliftant at the obfeivatory of Biida, has 

 made, in feveraf cities of Croatia, obfervations of great im- 

 portance to Geography. 



[To be concluded in the next Number.] 



V^Iir. Defcription of a Jingular Phenomenon in a Thunder- 

 Cloud. J5v L. C. LichtEnBerg*. 



o, 



'N a fummer's day, exceedingly hot and fultry, the ba- 

 rometer being at 27 inches feven lines, and Reaumur's ther- 

 mometer at 2i\, there was formed, about three in the after- 

 noon, to the north of Gotha, a dark thunder-cloud, having 

 the appearance of rocks piled upon each other, and in fhape 

 almoft like a mufliroom. (Plate i. Fig. i.) The magnificent 

 fpeclacle exhibited bv this immenfe mafs floating in the blue 

 expanfe of the atmofphere excited my attention ; and I foon 

 obferved, that, from the fmall part which reprefented the ftem 

 of the mufliroom, there arofe a fine bright vapour, which in 

 a few moments formed a perfeft ring around this part of the 

 cloud. The ring feemed to be in violent agitation, by which 

 it became always more enlarged, fo that in the courfc of a 

 minute it exceeded the greateft breadth of the upper part of 

 the cloud. It then began to extend itfelf upwards and down- 

 wards, and in lefs than thirty feconds the whole cloud was 

 enveloped in a tranfparent covering, (Fig. 2.) Tliis pheno- 

 menon had fcarccly continued a minute when the cloud 

 began to extend itfelf, as if by a current of air forced from 

 its interior, and to aflume the form of a fan. It now loft 

 its fmooth rim, which terminated, as it were, in fringes, 

 * From Mil? awn fur das Neurfte aus der Phvfik, Vol. I. 



Vol. VI. G and 



