FoJJil Bones, ^c. in tU Roei of Gibraltar, at I 



concretion is found of a reddifli brown ferruginous colour, with an earthy frailure and con- 

 fiderable induration, inclofing the bones of various animals, fome of which have the appear- 

 ance of being human. Thefe bones are of various fizes, and lie in all dire£lions intermixed 

 with fliells offnails, fragments of the calcareous rock, and particles of fparj all of which 

 materials are ftill to be feen in their natural uncombined ftates, partially fcattered over the 

 furface of the mountain. Thefe having been fwept by heavy rains at different periods from 

 the furface into the fituations above defcribed, and having remained for a long feries of years 

 in thofe places of reft, expofed to the permeating aftion of water, have become enveloped 

 in, and cemented by, the calcareous matter which it depofits. 



The bones in this compofuion have not the fmalleft appearance of being petrified ; and if 

 they have undergone any change, it is more like that of calcination than that of petrifac- 

 tion, as the moft folid parts of them generally admit of being cut and fcraped down with the 

 fame eafe as chalk. 



Bones combined in fuch concretions are not peculiar to Gibraltar ; they are found in 

 fuch large quantities in the country of Dalmatia, and upon its coafts in the iflands of Cherfo 

 and Ofero, that fome naturalifts have been induced to go fo far as to aflert, that there has 

 , been a regular ftratum of fuch matter in that country, and that its prefent broken and inter- 

 rupted appearance has been caufed by earthquakes or other convulfions experienced in that 

 part of the globe. But of late years, a traveller (Abbe Alberto Fortis) has given a minute 

 defcription of the concretion in which the bones are found in that country : and by his ac- 

 count it appears, that with regard to fituation, compofition, and colour, it is perfedly fimilar 

 to that found at Gibraltar. By his defcription it alfo appears that the two mountain rocks 

 of Gibraltar and Dalmatia confift of the fame fpecies of calcareous ftone ; from which it is 

 to be prefumed that the concretions in both have been formed in the fame manner and about 

 the fame periods. 



Perhaps, if the fiflures and caves of the rock of Dalmatia were ftill more minutely exa- 

 mined, their former communications with the furface might yet be traced, as in thofe de- 

 fcribed above ; and in that cafe, there would be at leaft a ftrong probability that the mate- 

 rials of the concretions of that country have been brought together by the fame accidental 

 caufe, which in my opinion has coUeded thofe found in the caverns of Gibraltar. I have 

 traced in Gibraltar this concretion, from the loweft part of a deep perpendicular fifTure up to- 

 the furface of the mountain. As it approached to the furface, the concretion became lefs 

 firmly combined; and when it had no covering of the calcareous rock, a fmall degree of ad- 

 hefion only remained, which was evidently produced by the argillaceous earth in its compofi- 

 tion having been moiftened by rain and baked by the fun. ^ 



The depth at which thefe materials had been penetrated by that proportion of ftala£titical 

 matter, capable of giving to the concretion its greateft adbefion and folidity, I found to vary 

 according to its fituation, and to the quantity of matter to be combined. In figures nar- 

 row and contraiSted, I found the concretion pofleffing a great degree of hardnefs at fix feet 

 from the furface ; but in other fituations more extended, and where a larger quantity of the 

 materials had been accumulated, I found it had not gained its greateft degree of adhefion at 

 double that depth. In one of the caves where the mafs of concretion is of confiderable fize, 

 I perceived it to be divided into different beds, each bed being covered with a cruft of the 

 ftalaftitical fpar from one inch, to an inch and a half in thicknefs ; which feems to indicate, 



that 



