On Gravlix, ^(.\ — Defcripthn sf Gibraltar. igj 



Remarks on the preceding Connnuriicat'ton. 

 UPON confuking the original, to which I referred by memory, in the note at page 85 of 

 the prefeiit volume, I perceive that both the paflages alluded to are in the tregtifc- De Facie 

 in OrbeLunaj. I was mifled by another obfcure paflage in the third book De PLicitfs 

 Philofophorum, under the title Tlipi kivmiu; yn;. ly. where it is faid that Philolaus the Pytha- 

 gorean held that the earth revolves in an orbit (■aepi ro •srt/f) around the fire, and that 

 Heraclides of Pontus and Ecphantus the Pythagorean attributed motion to the earth, not 

 progrefl'ive, but rotatory, from weft to eaft. I did not, as my learned correfpondent feenis 

 to intimate, pretend to fay that either Plutarch or the fpeakers in his treatife exhibited the 

 doflrines of the gravitating and projeftile forces, as being worthy of adoption. My implied 

 argument was, that fince they are extant in a paffage of fome length, there were in faiEt phiio- 

 fophers among the ancients who had maintained and developed them ; though, from a variety 

 of well known caufes, this doflrine remained without diftindlion among other ill-digefted or 

 falfe fyftems. The combination of thefe forces in the moon, which occurs in the paragraph 

 to which Theo replies, in my correfpondent's quotation, isuairotTn ftsv crtXwyi Pon9sia "apoirofitf 

 mtctiv, *i xivriffi; avTti kou ro pi^oihi Ttii vcpiayenyn;' D.a-'n'ip, &c. "But the moon is prevented from 

 " falling by its motion, and the violence of its revolution ; as bodies placed in a flin^ and 

 " whirled round do not drop out. For every body will be carried according to its natural 

 •' motion, if not diverted by fome other caufe. The moon is not, therefore, carried in the 

 *' dire£lion of (or by j its weight, becaufe its circular motion oppofes this tendency," 



AJhart Minerahgtcal Defcrlpt'ion of the Mountain of GibraUar. By Major Imrie*. ' 



X H E mountain of Gibraltar is fituated in 36° 9' north latitude, and in 5° ly'eafllonc^itude 

 from Greenwich. It is the promontory which, with that of Ceuta upon the oppofite coafl 

 ofBarbary, forms the entrance of the ftraits of Gibraltar from the Mediterranean; and 

 Europa Point, which is the part of the mountain that advances moft towards Africa, is 

 generally regarded as the moft fouthern promontory in Europe. The form of this moun- 

 tain is oblong ; its fummit a (harp craggy ridge ; its direction is nearly from north to fouthf 

 and its greateft length in that diredtion falls very little (hort of three miles. Its breadth^ 

 varies with the indentations of the fhore, but it no where exceeds three quarters of a mile. 

 The line of its ridge is undulated, and the two extremes are fomewhat higher than its 

 centre. 



The fummit of the Sugar-loaf, which is the point of its greateft elevation towards the 

 fouth, is 1439 f^^^ » ^^^ Rock Mortar, which is the highcft point to the north, is 1 350 ; and 

 the Signal-houfe, which is nearly the central point between thefe two, is 1276 feet above the 

 level of the fea. The weftern fide of ths mountain is a feries of rugged flopes, interfperfed 

 with abrupt precipices. Its northern extremity is perfedlly perpendicular, except towards 

 the north-weft, where what are called the Lines intervene, and a narrow paffage of flat 

 • Tranfaftions of the Royal Society of Edinburgh, iv, 191. 



Vol. IL—Julv 1798. B b ground 



