640 RECORDS. 



Summary of Papers. 



The paper by Professor Rees was illustrated by lantern views, 

 among which were several of the Yerkes Observatory in Wiscon- 

 sin, showing not only the great telescope itself, but also the 

 very large dome required in which to mount it. The author 

 then pointed out the problem that the French astronomers had 

 set before them, viz, to construct a telescope that should far sur- 

 pass the great Yerkes instrument. In order to avoid attempting 

 the construction of a dome for a telescope having a focal length 

 of 200 feet, which would be out of the question, they are build- 

 ing their telescope in a fixed horizontal position, directing the 

 light into it by means of a mirror that may be so moved as to 

 follow the course of a star and so called a siderostat. Professor 

 Rees showed views of the details of the mirror, its mechanism 

 and the methods of polishing it. The object glass of the tele- 

 scope will be about 49 inches in diameter, and when the instru- 

 ment is completed, it will be the largest in the world. 



Mr. Dudley in his paper showed that most of the heavy modern 

 rails are held so tightly by the bolts through the splices, that 

 when great falls of temperature occur, they may break, through 

 an excessive tensil strain, before they can "render" in the 

 splices. On a rise of temperature, strains of compression are set 

 up, so that nearly all breakages occur on a drop in temperature. 



R. Gordon, 

 Secretary. 



SECTION OF BIOLOGY. 

 March 13, 1899. 



Section met at 8 P. M., Professor Lee, presiding. 



The minutes of the last meeting of the Section were read and 

 approved. 



The following program was then offered : 



F. B. Summer, Observations on the Germ Layers of 

 Teleost Fishes. 



H. L. Clark, Further Notes on the Echinoderms of 

 Bermuda. Paper presented by Professor C. L. Bristol. 



