18 KEPORT OF THE SECRETARY. 



the construction of a silvered glass telescope, accompanied bv a paper 

 by Prof. (i. W. Kitchey on the modern reflecting telescope and the 

 making- and testing- of optical mirrors. 



For few papers published by the institution has there been a more 

 constant demand than for this memoir by Prof. Henry Draper, entitled 

 '•'On the Construction of a Silvered Glass Telescope," originally issued 

 forty years ago, in 1864. The paper is of remarkable merit as a sum- 

 mary of, and an addition to, the knowledge existing at the time, but 

 during the long interval which has elapsed, progress has been made 

 in various directions and by various hands. On the occasion of a new 

 edition of this classic memoir, it was sought to give an account of the 

 latest knowledge on the subject, and I was gratified to be able to obtain 

 from Mr. Ritchey, whose labors in this direction are so well known, 

 an account of the processes which he has employed for making the 

 great mirrors that have been so effective at the Yerkes Observatory, 

 and it has been decided to republish, with the original Draper memoir, 

 but as an entirely independent contribution to the subject, the present 

 article by Mr. Ritchey. The great refracting instruments which have 

 been produced in recent years have not superseded the use of the 

 reflector, which, on the contrary, is occupying a more and more impor- 

 tant place. The reader is here presented with the most recent methods 

 and results needed in the construction of great mirrors for modern 

 reflecting telescopes. 



The work on whales is by Dr. Frederick W. True, head curator of 

 Biology in the National Museum, and treats in an exhaustive manner 

 of the whalebone whales of the western North Atlantic compared with 

 those occurring in European w^aters, with some observations on the 

 species of the North Paciflc. It makes a volume of 337 pages, with 

 50 full-page illustrations and 97 text flgures. 



Doctor True has here brought together ext^^nsive original data rela- 

 tive to the external and osteological characters of the large whales of 

 the western North Atlantic, for the purpose of determining whether the 

 species are the same on both sides of that ocean. The facts have l)een 

 derived from a study of fresh specimens art the Newfoundland whaling- 

 stations, the collection of the United States National Museum, and the 

 skeletons in other large museums of the United States. Special study 

 was given to the type specimens of American species proposed ])y 

 Prof. E. D. Cope and Capt. C. M. Scammon, all of which, Avith one 

 exception, were examined l)y the author. 



The investigation is preparatory to a study of the geographical dis- 

 tribution and migrations of the larger cetaceans in the North Atlantic, 

 which could not be undertaken until the identity of the species them- 

 selves was detei-mined. Numerous facts, however, relating to the 

 occurrence of whales at different points off* the coasts of North 

 America and the seasons of their appearance and disappearance, have 



