62 BULLETIN OP THE 



Bpecimen, a system of ridges is crossed at right angles by another 

 of smaller size, a reticulation being the result. 



A dilTerent explanation is given by Jukes {loc. cit.}, and by 

 Dana (Manual, 1874, p. 672). 



3. As to their Geological Interpretation. — If currents are 

 adequate to their production, they may be formed at great depth, 

 and are demonstrative neither of shallow water nor of the prox- 

 imity of shore, as they are often regarded. They are never found 

 in shales, while few sandstone series are without them. That is, 

 they are formed only where the motion of the water is too great 

 to admit of the accumulation of fine sediment. 



Mr. F. "W. Putnam, of Salem, Mass., described and explained 

 ripples formed by the tide. 



Mr. Powell described various forms of ripple-marks which he 

 had observed, and remarked that ripple-marks may be formed in 

 deep water from the motion of waves on the surface, and were 

 not necessarily an indication of action on a shore. 



The subject was further discussed by Messrs. Henry, Abbe, 

 and Gilbert. 



Mr. J, J. Woodward made some comments on 



THE MICROSCOPICAL STRUCTURE OF WOOL : 



reading a report, by Dr. John LeConte and himself, to the 

 President of the National Academy of Sciences, on the micro- 

 scopical examination of many specimens of mixed goods of sheep 

 or lamb wool, with cow or calf, and other hair, with a view to 

 determine the proportion of the former. In illustration, he ex- 

 hibited on a screen 25 photographs of various kinds of wool and 

 hair. 



The examination and report were made at the request of the 

 Hon. Secretary of the Treasury, in order to determine the rate 

 of duty on the several kinds of goods. 



97th Meeting. December 18, 1875- 



The President in the Chair. 

 Fifty members and visitors present. 



