Roy a I I?ist it u t ion . 1 SS 



plates, containing accurate delineations of a great number 

 of curious fossil vegetable remains coloured after nature. 

 In a future number we shall give a further account of this 



useful and valuable work. 



. 



"Shortly will be published a new Edition, with improve- 

 ments, of 



The Magnetic Atlas, or Variation Charts of the whole ter- 

 raqueous Globe, comprising a System of the Variation 

 and Dip of the Needle, on the Projection of the former 

 Editions, by John Churchman, Fellow of the Russian 

 Imperial Academy of Sciences. 



This plan represents on a plane as truly as on a globe the 

 necessary proportions of every country, and the true nature 

 of every curve. The improvements of the new edition will 

 .consist principally of J lalleian lines drawn through all the 

 different places where the degree both of variation and dip 

 are the same, and thus avoiding the trouble of measuring 

 angles. These charts will be found to possess great advan- 

 tages, particularly in cloudy weather ; for the darkest day at 

 sea often shows the sun long enough at noon to observe the 

 latitude. Or the dip alone (being easily found at all times) 

 is sufficient near the land, as the lines of equal dip inter- 

 sect every part of any coast in certain latitudes. Thus the 

 difficult problem of the longitude may be determined at sea 

 by two different methods : 1st. From a true knowledge of 

 the latitude and variation: 2d. Of the latitude and dip.. 

 Perhaps no observation, except the dip, can be taken so fre~- 

 quently as the variation. That a mean of these observa- 

 tions- can be found accurately enough at sea, many expe- 

 rienced navigators have already borne witness; the only 

 difficulty arising from the iron on ship-board giving some- 

 times a false direction to the needle, may be overcome by 

 ascertaining the magnetism of the ship. 



XLIX. Proceedings of learned and Economical Societies, 



IU)YAL INSTITUTION. 



At a special meeting of the managers and visitors, held 

 the 1 fth day of May 1 S04, 

 The Duke of Somerset" in the chair, 

 The following address to the proprietors, subscribers, and 

 others, respecting a proposed mineralogical collection, 

 and office of assay, was read, approved, and ordered to be 

 circulated ; - • ' • - ' 



U 4 In 



