220 Notices respecting New Books. 



The column is thin, composed of short cylindrical joints, but 

 the articulating surfaces are not distinctly seen in the speci- 

 men under examination ; the enlarged apex is reversed coni- 

 cal, formed of 5 joints, the basal one is very small, and thin ; 

 the second, third and fourth, each gradually larger and thicker : 

 the fifth is nearly of the same height, but rather larger in dia- 

 meter, and the upper part is divided into 5 articulating sur- 

 faces, each marked with five radiating grooves, and finely cre- 

 nated on the margin. The pelvic plate small, wedge-shaped ; 

 the outer edge is pentangular, outer sides very short. The 

 first and second set of costals are broad and nearly equal ; 

 the scapulars arfi as thick as the costals in the centre, and 

 shelving on each side ; the arms, two from each scapular, com- 

 pressed, each furnished with a double series of thin jointed 

 filiform tentacula, the first joints of the arm are similar to the 

 first costals, and the joints of the appendages are thin and 

 compressed, similar to those in the arms of Comatula. 



In the above description I have adopted the name of the 

 parts used by Miller. For the knowledge of this species I am 

 indebted to the kindness of Mr. J. S. Pratt of Bath, by whom 

 it was found. The specimen is placed in the collection of the 

 British Museum. And I have ventured to name the species 

 after that gentleman, although he disclaims being the first dis- 

 coverer of it : but I consider that he is justly deserving of the 

 honour, as being the first person who enabled it to be made 

 public, and presented a specimen for the purposes of science 

 to the National Collection. 



XXXIX. Notices respecting New Booh. 



A Popular Sketch of Electro- Magnetism, or Electro-Dynamics ; ivitk 

 Plates of the most improved apparatus for illustrating the principal 

 phcenomena of the science ; and outlines of the parent sciences Elec- 

 tricity and Magnetism. — By Francis Watkins, Curator of Phi- 

 losophical Instruments in the University of London. London, 8vo. 

 pp. 83. Three plates. 



THIS work, we believe, is the first attempt that has been made 

 to give a popular, and at the same time a comprehensive view 

 of the new science of electro-magnetism. The notices of this 

 science given in some of our elementary works on natural philoso- 

 phy and chemistry, are necessarily brief and partial; and Professor 

 Cumming's translation of Demontferrand's Manuel d 1 Electricite Dy- 

 namique, is adapted chiefly to the use of those who are accustomed 

 to mathematical expressions. The writer of this " Popular Sketch " 

 therefore, deserves commendation for having thus endeavoured to 

 make this beautiful and interesting department of knowledge, a 



branch 



