J^otice of a singular impression in sand stone, 1 55 



Art. XXI II. — Notice of a singular impression in sand 

 stone,* by Mr. Isaac Lea. 



Philadelphia, Feb. 24, 1822. 



PROFESSOR SILLIMAN. 



Dear Sir, 



On looking over my port folio a few days since, 1 found 

 a drawing of some reliquia which I made a few years since, 

 when I observed them about a quarter of a mile above 

 Pittsburgh, and on the same side of the Monongahela. 



With this I send you a copy of the drawing, which you 

 will please to insert in the Journal of Science, if you think it 

 worthy of a place in that useful work. I am more anxious 

 to see this figure in a permanent place, as on a late visit 

 to it I found the dilapidating hammer of the quarry-man, to 

 be likely to remove from its native bed, and destroy one 

 of the most singular specimens of the kind which I have ev- 

 er seen, and respecting which, the learned find so much 

 difficulty in deciding whether it belongs to the animal or 

 vegetable kingdom. 



The impression is very perfect on a sand stone rock, and 

 entirely flat. The base is perfectly terminated in the rock 

 and is about six inches across ; its length three feet, and ter- 

 minated by a fracture of the rock, which leaves it doubtful 

 how long it may have been in its pristine state ; at this frac- 

 ture it is four inches broad. The two lines are distinct in 

 both lozenge shaped impressions, which are represented of 

 the natural size in fig. 2d. [See the plate at the end.] 



The hill in which it exists is not sufficiently high to take 

 in the bed of coal pervading the neighbouring hills in a hor- 

 izontal stratum about two hundred and fifty feet above this 

 locality. In fragments of the same rock, are found many 

 impressions resembling culmiferous plants, the joints of 

 which are perfect. Some of them are now in my own col- 

 lection, others I deposited, particularly a large one, in tl:^e 

 "Academy of Natural Science." 



Your obedient servant, 



ISAAC LEA. 



* Note — This article should in strictness, have been placed under the 

 Geology, &c, but having been accidentally omitted, is inserted here. 



