Geology and Mineralogy. 411 



similar curves without reaching the maximum points attained by 

 gold and silver. It is possible to deduce the dispersive power of 

 the metals and to compare their indices of refraction with those 

 experimentally determined by Kundt. The agreement has been 

 found in most cases to be close. — Nature, April 4, 1889, p. 552. 



J. T. 



II. Geology and Minekalogy. 



1. Recent discoveries in the Carboniferous Flora and Fauna of 

 Rhode Island. — During the past spring (1S88) the museum of 

 Brown University was enriched by the donation of a valuable 

 collection of fossil plants presented by the Rev. Edgar F. Clarke 

 of Providence, R. I., who found them in a thin layer of car- 

 bonaceous shale at Pawtucket. These were sent to Prof. Leo 

 Lesquereux for identification.* Besides the plants, several fossil 

 cockroaches of two genera, and the remains of an Arthrogastrous 

 Arachnidan of the genus Architarbus, have been found by Mr. 

 Henry Skolfield and others in the Pawtucket bed. These are in 

 Mr. Scudder's hands for description. In addition Mr. Skolfield 

 has been fortunate enough to discover in the same beds the 

 impression of an Annelid worm, several shells of Spirorbis, and 

 what appears to be the track of a gastropod mollusc ; he has 

 kindly placed these in the hands of the writer for examination. 



It will be remembered that until very recently no animal 

 remains had been known to exist in the beds of the Rhode Island 

 coal basin, but now, chiefly through the zeal and industry of Mr. 

 Clarke, there have been discovered representatives of the class of 

 worms, molluscs, arachnids and insects ; while the age of the 

 beds has been established with a greater degree of certainty than 

 ever before. Mr. Lesquereux, in a letter to the undersigned, 

 remarks : " These specimens taken altogether are interesting as 

 indicating, more than any other lot of fossil plants of Rhode 

 Island I have seen, the stratigraphical relation of your coal strata 

 to those of the part of the Anthracite measures of Pennsylvania, 

 where, even, I have not observed such a predominance of species 

 of Odontopteris, typically allied to those described by Fontaine 

 and White from the UppeV Carboniferous of Pennsylvania." 



Providence, Aug. 18, 1888. •> A. S. PACKARD. 



2. Annual Report of the Geological Survey of Arkansas for 

 1888; by John C- Beannee, Ph.D., State Geologist. 320 pp. 

 8 vo. .^Little Rock, Arkansas, 1888. — The first volume of this 

 Geological Report, contains, besides the administrative report of 

 Professor Branner, a report on the geology, and especially the 

 economic geology, of the central western part of Arkansas by Dr. 

 T. B. Comstock. The geological results are mostly deferred to 

 another volume, while the various mining regions and their 

 products are described with fullness. Two maps accompany 



* The list of plants received from Prof. Packard will be found on page 229 of 

 this volume. This note should have accompanied it. 



