346 



SCIENCE. 



[N. S. Vol. IV. No. 89. 



photosphere is examined, and evidence is 

 brought forward from recent direct visual 

 observations (Howlett, Sidgreaves, Spoer- 

 er) , from the rate of solar rotation deduced 

 from faculse, spots, and surface (Duner), 

 and from the thermal absorption over spots, 

 to support the view that spots may be 

 masses of absorbing gases above rather 

 than below the photosphere. The paper 

 will be published in the Astrophysical Jouf- 

 nal. 



Sedenions : By James B. Shaw; presented in 

 outline by Prof. E. W. Hyde. 

 If q be any quaternion, (P the operator 

 on q such that if 



q = w + xi + yj+ zk, 

 $ g ■= (a'w + bh -\- c^y -\- d^z) 

 + (a"w + U'x + &^y + (?'2!)i 

 + (a™M7 + h^x + <^'y + d'^'z) j 

 + (a^^w + V"'x + &^y + d^'z) k. 



^ is called a Sedenion. The paper (offered 

 for publication in the Bidletin of the Ameri- 

 can Mathematical Society) is a development of 

 the elementary formulae of Sedenions con- 

 sidered as an algebra of sixteen units. These 

 formulae are developed by the aid of Qua- 

 ternions. 

 On the Distribution and the Secular Variation 



of Terrestrial Magnetism, No. IV: On the 



Component Fields of the Earth's Magnetism : 



By L. A. Bauer. 



This paper, to appear in Terrestrial Magne- 

 tism, continues the researches hitherto pub- 

 lished by the author, and is an attempt to 

 resolve the prevailing magnetic field of the 

 earth into its components. The paper was 

 illustrated by maps and diagrams. 



Determination of the Weights of Observations : 



By J. E. Eastman. 



A brief account was given of a method of 

 determining the weights to be used in com- 

 bining the results of observations made in a 

 series of years with the same instrument 

 (meridian circle) . The results also showed 

 the futility of excessive repetition of an ob- 

 servation with a view to increased accuracy. 



On the Composition of Simidtaneous and Succes- 

 sive Vectors: By Alexander Macfar- 



LANE. 



Vector Algebra is commonly founded 

 partly on physical ideas, partly on arbitrary 

 formal laws. The author prefers to give it 

 a purely geometrical or physical basis. 

 The sum of simultaneous vectors is com- 

 mutative, because they have no real order ; 

 the sum of successive vectors is not com- 

 mutative, because they have a real order. 

 The square of a sum of successive vectors 

 differs from the square of a sum of simul- 

 taneous vectors by a set of terms depending 

 on the order of the succession. This was 

 illustrated by the generalized form of the 

 Exponential Theorem for space. 



All the papers on the program having 

 been read, at the conclusion of the session 

 on Wednesday afternoon, August 26th, 

 Section A adjourned. 



Edwin B. Frost, 



Daetmouth College. Secretary. 



SECTION B— PHYSICS. 



The address of the Vice-President, Carl 

 Leo Mees, upon Electrolysis and some Out- 

 standing Problems in Molecular Dynamics, will 

 be printed in this Journal. 



The meetings of the section were full and 

 interesting. One of the sessions was inter- 

 rupted by the introduction of Dr. Chas. E. 

 West, of Brooklyn, a founder of the Asso- 

 ciation, who gave reminiscences of Joseph 

 Henry and exhibited a small helix made by 

 Prof. Henry and used by him in conjunc- 

 tion with Dr. West on July 10, 1842, to 

 magnetize needles during a thunder storm. 

 Dr. West also exhibited a fragment of 

 wood from the ship of Captain Cook, given 

 him by the elder Silliman sixty years ago. 

 The remarks of Dr. West were listened to 

 with profound interest and the section 

 tendered to him a vote of thanks. 



The section enjoyed a visit to the home 

 of Mr. Edgar B. Stevens, a manufacturer 



