318 ANNUAL OF SCIENTIFIC DISCOVERY. 



of the woody stem as perfectly as the finer varieties of silicified Avood, and 

 what is chiefly important, the details of structure are the same in both speci- 

 mens. The most prominent characters under the microscope, are 



1. The mass consists of elongated cells, withareolar markings, and includes 

 few or no proper ducts. 2. These cells are intersected by thin, medullary 

 plates, composed of short cells, with similar, but more scattered markings. 

 3. The areolse of the elongated cells are arranged in a single, very rarely a 

 double row, on each side of the two faces which are parallel to the medullary 

 plates, but are entirely absent from the other faces of the cells. In all these 

 particulars, as well as in the dimensions of the cells, and the size and form 

 of the areola?, Professor Rogers considered the structure of these lignites as 

 closely agreeing with that of the fossil coniferous wood described and figured 

 by "Witham, under the name of Pence Huttonia and P. Lindleiana. This fos- 

 sil genus, almost identical in woody structure with the modern pine, was 

 found by Witham to be restricted to rocks of the Oolitic period. Hence the 

 characters of these lignites, while they furnished a new evidence in favor of 

 the view which Professor Rogers has heretofore maintained of the near af- 

 finity in time of the so-called new red sandstone, or Triassic rocks of this 

 country, and the coal-bearing deposits of eastern Virginia and North Carolina, 

 helped to confirm his conclusion that both these belts belong to a period cor- 

 responding to the lower part of the Oolite or Jurassic series of Europe. Pro- 

 fessor Rogers added that these lignites appear to be identical in structure 

 with that variety of silicified wood found in the coal-bearing rocks of eastern 

 Virginia, to which he had formerly referred when speaking of the Jurassic 

 age of these deposits. 



ON THE FORMATION OF FOSSIL EAIX-DEOPS. 



At a recent meeting of the Boston Society of Natural History, Professor 

 Jeffries "Wyman exhibited some of the results on experiments on the forma- 

 tion of rain impressions in clay ; from which it appears that ordinary rain 

 marks are characterized by the existence of radiating lines around the circum- 

 ference of the impressions, which are caused by the fragments of the drops 

 as they are dispersed often impinging upon the plastic surface. If a mass of 

 water is thrown into the air and allowed to fall on soft clay, the form of the 

 impression will depend upon the condition of the drops at the time of con- 

 tact. In descending, the drops assume the following forms, viz. : first, that 

 of the flattened sphere ; second, that of a cup with the concavity downward ; 

 third, that of a ring ; and fourth, those of two or more spheres formed by the 

 rupture of the ring. If the sphere be above a certain size, the impression 

 presents a reticulated appearance in the center, with radiating lines around 

 the circumference. The impression formed by the cup is reticulated in the 

 center without radiating lines. The ring forms an impression corresponding 

 with its shape, with radiating lines on its inner border, and sometimes on 

 its center border. Professor "VVyman thought that rain marks could be dis- 

 tinguished from those of spray. The rain mark is modified by the condition 

 of the surface on which it strikes ; if the latter is hard, or of a coarse material, 



