Royal Physical Society. 461 



rock will, however, cause some surprise ; and we naturally ask 

 what can this lithographing property be \ This and many 

 other questions must be passed, and the uppermost thought 

 attended to ; for w T e are looking back upon the ancient periods 

 in the history of our earth. I have found in most of our rock 

 formations plant-like forms "painted," or rather "discharged" 

 out. When cleaving the Devonian and Silurian rocks of 

 Cornwall, and the Old Red Sandstones of Caithness and Ork- 

 ney, they have often occurred, and I have been struck by their 

 forms ; for so like plants have they appeared, that again and 

 again I have found great difficulty in persuading myself that 

 they were not plants, always pleading the absence of organic 

 matter. This was a sad stumbling-block, for not a vestige 

 could be seen. Others have been equally perplexed. Our 

 lamented friend, Mr Hugh Miller, after speaking of the now 

 acknowledged land-plants of the Lower Old Reel Sandstone of 

 Caithness, &c, says, at page 435, " Testimony of the Rocks," 

 — " I may here mention, that curious markings, which have 

 been regarded as impressions made by vegetables that had 

 themselves disappeared, have been detected during the last 

 twelvemonth in a quarry of the Lower Old Red Sandstone 

 near Huntly, by the Rev. Mr Mackay of Rhynie. They 

 are very curious and puzzling ; but, though some specimens 

 present the appearance of a continuous midrib, that throws 

 off, with a certain degree of regularity, apparent leaflets, I am 

 inclined to regard them rather as lying within the province of 

 the ichnologist than of the fossil botanist." , 



From never having seen any of my friend the Rev. Mr 

 Mackay's " puzzling specimens," I am unablerto give a de- 

 cided opinion about them ; but from the tenor of the passage 

 (of which I have only quoted a part) I should be inclined to give 

 them to the botanist. The absence of " vegetable" matter, 

 with the " mid-rib" and " hard fern"- like appearance, weigh 

 greatly with me now ; for, as with the fossil, so with the 

 beautiful recent Stromness forms — no portion of the vegetable 

 can now be seen. There is plenty of proof that the Stromness 

 pictures now presented to your notice were made by plants. 

 I tried, on my return home, the experiment of laying a piece 

 of Desmarestia on a stone from the beach, and exposed it in 



