Fata lilorgana.— Concretions of Volatile Otis, izy 



■which I have copied, is: i. That by the fituation of the Faro of McfTina, the current 

 from the fouth, at the expiration of which this phenomenon is moft likely to appear, is fo 

 far impeded by the figure of the land, that a confiderable portion of the water returns 

 along fliore. 2. That it is probable the fame coafts may have a tendency to modify the 

 low-er,portion of the air in a fimilar manner, during the fouthern breeze ; or, in other 

 words, that a fort of bafon is formed by the land, in which the lower air is more difpoled 

 to become motionlefs and calm than elfewhere. 3. That the Morgana Marina prefents 

 inverted images below the real objects, which are multiplied laterally as well as vertically; 

 and that there are repetitions of the fame multiplied objefls at more confiderable vertical 

 intervals. This I gather from the appearance of the dome and other obje£ls in the plate. 

 4. That the Aerial Morgana is not inverted, but, as I am dlfpofed to conjecture, is more 

 elevated than the original obje£ts. 5. That the fringes of prifmatic colours are produced in 

 falling vapours, fimilar to many appearances which have been defcribed by authors, but not 

 accurately explained by the general principles of refraftion through fpheres of water. The 

 £hip is referred to by the author as an obje£t furrounded by thefe fringes : whence it 

 appears that the colours apply to the dire£l rays from objects, as well as to thofe of the 

 Marine Morgana. 6. Various other objeiO:s in the drawing, as well as in the defcription, 

 afford matter for queflion and conjetlure, but none perhaps which it may be proper to 

 enlarge upon, until the theory be better known. 7. It feems at all events more probable 

 that thefe appearances are produced by a calm fea, and one or more ftrata of fuper- 

 incumbent air differing in refraftive, and confequently refiedUve power, than from any 

 confiderable change in the furface of the water, with the laws of which we are much better 

 acquainted than with thofe of the atmofphere. 8. By attentive refle£lion upon the fa£ls 

 and reafonings in Mr. Huddart's paper *, we may form a theory to account for the ere£t 

 and inverted images : the polifhed furface of the fea may perhaps account for the vertical 

 repetition ; but for the lateral multiplication we mud have recourfe to refle£ling or 

 refradling planes in the vapour, which appear nearly as difficult to deduce or eflablifh, as 

 thofe which have been fuppofed on the water. 



VIII. 

 ^ Memoir containing /onre Refults arifingfrom the ABion of Cold on the Volatile Oils, and an 

 Examination of the Concretions found in feveral of thofe Oils. By Cit. JIIa-RGUERON, 

 Member of the Societe des Pharmaciens at Paris. 



[Concluded from page 186 ] 



An Examination of the Concretions found in feveral Volatile Oils. 



A HE volatile oil of fennel-feed, which had been long made, had depofitcd a concretion 

 of a lamcUatcd form. The oil was of an amber-colour, and fmcll fcarcely perceptible. It 

 was fluid, and no longer capable of afluming the concrete flate at the temperature of four 

 or five degrees below congelation. The concr^'tc matter being fcparated was ycllowifh, 

 ar.<J had the tafte and fmcll of fennel. When expofcd to the aii it became dry and friable 



* Pliilofopliical Journal, I. 145. 



G g 2 betwffn 



