REPORT OP THE SECRETARY. 21 



in long periods. The paper commences with an abstract of those on 

 the declination. To these are added the latitudes and longitudes of 

 the places observed. 



The observed magnetic variations, at the different places, have 

 been reduced to the epoch of January, 1842, .by adding the annual 

 increase, namely 2' 7, found by comparing the observations of 1S40 

 with those of 1862. An elaborate discussion of the horizontal force 

 furnishes a comparison of European and American results. The de- 

 ductions from the observations on the dip of the needle are given 

 in terms of geographical latitude and longitude, and the isoclinal 

 lines or lines of equal dip are protracted on a map which also con- 

 tains the lines of equal magnetic force, both in regard to its 

 horizontal and total intensity. Three of the stations visited by Mr. 

 Schott fell within the scope of the coast survey; and the expense of 

 the redetermination of the magnetic elements, at these points, was 

 defrayed by the superintendent of that work; the determinations at 

 the remaining stations were at the expense of the Smithsonian Insti- 

 tution. 



An account of the other papers in this volume has been given in 

 the previous report. 



Miscellaneous Collections. — Several series of articles forming parts of 

 the series of Miscellaneous Collections, as stated in previous reports, 

 have been undertaken, of which some have been completed, some are 

 still in hand, and others have been printed during the past year. 



The first of these series is that relating to the shells of North 

 America, and will consist of the following works : 



1. Check lists of North American shells, by P. P. Carpenter, &c. 



2. Circular relative to collecting shells.. 



3. Elementary introduction to. the study of conchology, by P. P. 

 Carpenter. 



4. List of the species of shells collected by the United States ex- 

 ploring expedition, by the same author. 



5. Descriptive catalogue of the shells of the west coast of the 

 United States, Mexico, and Central America, by the same author. 



6. Descriptive catalogue of the air-breathing shells of North 

 America, by W. G. Binney. 



7. Descriptive catalogue of several genera of water-breathing 

 fresh-water univalves, by the same author. 



8. Descriptive catalogue of the Melaniadae. or the remainder of the 

 water-breathing fresh water univalves, by George W. Tryon. 



