OF ARTS AND SCIENCES. 251 



to Zoology. Intended for the College and the Parlor. Elements 

 of Ornithology. With Plates. 1 vol. 12mo. Boston. 1847. 



History of the Town of Medford, Middlesex County, Massachu- 

 setts, from its First Settlement in 1630 to the Present Time, 1855. 

 By Charles Brooks. 1 vol. 8vo. Boston. 1855. 

 The Commissioners of the Public Library. 



Proceedings on the Occasion of Laying the Corner-Stone of the 

 Public Library of the City of Boston. 1 vol. 8vo. Boston. 1855. 

 S. L. Abbot, M. D. 



Report of the Board of Trustees of the Massachusetts General 

 Hospital. Presented to the Corporation at their Annual Meeting, 

 January 23, 1856. 8vo pamph. Boston, 1856. 

 Royal Academy of Sciences, Stockholm. 



Ofversigt af Kongl, Vetenskaps-Akademiens Forhandlingar- 

 Tionde ArgSngen, 1853 ; Elfte ArgSngen, 1854. 2 vols. 8vo. 

 Stockholm. 1854 - 55. 



Four Uunclred and twenty-sixtli meeting. 



April 8, 1856. — Monthly Meeting. 



The Academy met at the house of the Hon. John C. Gray, 

 The President in the chair. 



The Corresponding Secretary read a letter from Dr. J. P. 

 Kirtland of Cleveland, Ohio, accepting Fellowship. 



Mr. G. P. Bond presented a paper " On the Use of Equiva- 

 lent Factors in the Method of Least Squares," which, on 

 motion of Professor Levering, was referred to the Committee 

 of Publication. 



Professor Eustis exhibited an apparatus illustrating a pecu- 

 liar case of warped surfaces. The apparatus consisted of two 

 planes at equal distances from each other, having upon their 

 contiguous surfaces, and opposite to each other, figures of an 

 ellipse. From the whole circumference of each of these 

 ellipses cords were tightly drawn obliquely across to a corre- 

 sponding but opposite point in the other. The eftect, on 

 looking through an aperture in the middle of the apparatus, 

 was a very peculiar series of curves, resulting from the cross- 

 ing of so many straight lines. 



