IjS Oji the life aj Oak Bark in dyeing Blacii 



We are equally ignorant in regard to the folar atmofpTierey 

 which is faid to give rife to the fo called zodiacal light. In 

 that cafe, however, it mud not be of a globular form, like our 

 atmofphcre, but extend round the fun's body like a kind of 

 zone. From this folar atmofphere M. Mairan * deduces the 

 northern lights ; but this opinion has been, in fome meafure, 

 refuted by d'Alembertf. 



The refult of what has been here faid, is, that refpefting 

 the atmofpheres of the celeftial bodies we know very little ; 

 and as the obfervations on this fubjeft require to be made 

 with the utmoft accuracy and attention, it will be a long^ 

 time before our knowledge on this head can be much en- 

 larged. It is to be hoped, however, that thofe who poflefs 

 acutenefs of fight, and good inftruments, will endeavour to 

 determine this point, for which no perfon feenis fitter than 

 Dr. Herfchel. 



XIII. On the Advantages ivhich refult from fuhjlituting 

 Oak Bark for Gall Nuts in dyeing Black, efpecially in 

 dyeing Hats. 



iMO Stephanopoli, a Corfican, and a fargeon in 

 tlie French army fo far back as the year 1783, propofed oak 

 bark as a fubditute for galls ; and the examination of his 

 procefs was referred by the Government firft to Macquer, 

 who gave a favourable report of the refult, and afterwards to 

 BerthoUet, who was of a different opinion. Several other 

 means for determining the advantages or difadvantages likely 

 to refult from a general adoption of the procefs were had re- 

 courfe to. Lately it was revived by the Lyceum of the Arts, 

 from whofe report we extraft the following account : — 



" Experiments were made, by order of the College of 

 Pharmacy, at the manufaftorv of Beaujolin and Morel. 

 Two boilers, of about two hundred and twenty hats each, 

 were made ready, one for the gall nuts and the other for the 



* See his Traitc Phyfique tt HiHorique de TAurore Boreale, fecond 

 edit. -Pan's 1754, 410, 



f See his Opufcules Mathematiques, Vol, VI. p. 335. 



8 ' bark, 



