40 Gee, Da/ton's Lectures and Lecture Illustrations.. 



Sheet 81. 



(29" x 21".) Explains the production of tides. 



Sheet 82. 



( l 7" x Si"-) Shows a beam of light from the sun 

 falling on a surface placed at right angles to the beam, 

 and the spreading of the beam when it falls on a hori- 

 zontal surface. 



Sheet 83. 



(21" x I7j") This is designed to explain the relation 

 between latitude and the sun's altitude. 



Sheet 84 



(8" X 8".) Represents the projection of a sphere with 

 meridians and circles of latitude. 



[Sheets 10, 33, 45> and nine others remain unclassified.] 



