U CONTENTS. 



Page 

 VI. Contributions towards Establishing the Ge- 

 neral Character of the Fossil Plants of the 

 g-enus Sigillaria. By William King, Esq., 

 Curator of the Museum of the Natural His- 

 tory Society of Newcastle-on-Tyne. Com- 

 municated by the Author. Continued from 

 Vol. XXXVI., page 290, . . , 62 



VII. On the Action of Yellow Lig'ht in producing" 

 the Green Colour, and Indigo Light the 

 Movements of Plants. By D. P. Gardner, 

 M.t)., Cor. Memb. Lye. Nat. Hist., New 

 York, ..... 76 



1. On the Production of Chlorophyl by Yellow 



Light, 76 



2. On the Movements of Plants towards Indigo 



Light, 82 



3. Some Applications of the preceding Facts, &c. 88 



VIII. Memoir of the late Mr William Blackio, Opti- 

 cian. By John Coldstream, Leith. Com- 

 municated by the Royal Scottish Society of 

 Arts, ..... 94 



IX. Description of Portable Levelling Instru- 

 ments. By David Stevenson, F.R.S.E., 

 F.R.S.S.A., Civil Engineer, Edinburgh. 

 Communicated by the Royal Scottish So- 

 ciety of Arts. With a Plate, . . 99 



X. Some Account of Levelling Instruments, with 

 Description of one of an Improved Form. 

 By Thomas Stevenson, Civil Engineer, 

 Edinburgh. Communicated by the Royal 

 Scottish Society of Arts, . . . 101 



XI. An Inquiry into the Nature of the Simple 

 Bodies of Chemistry. By David Low, 

 F.R.S.E., Professor of Agriculture in the 

 University of Edinburgh, . . . 107 



XII. Notice of the Employment of the Flesh of 



