CONTENTS. 



XII. On double Images caused by atmospherical Refraction. By 

 William Hyde Wollaston, M. D. F. R. S. - p. 239 



XIII. Investigation of the Powers of the prismatic Colours to beat 

 and illuminate Objects ; with Remarks, that prove the different 

 Refrangibility of radiant Heat. To which is added, an Inquiry 

 into the Method of viewing the Sun advantageously, with 

 Telescopes of large Apertures and high magnifying Powers. 

 By William Herschel, LL. D. F. R. S. - p. 255 



XIV. Experiments on the Refrangibility of the invisible Rays of the 

 Sun. By William Herschel, LL. D. F. R. S. - p. 284 



XV. Experiments on the solar, and on the terrestrial Rays that 

 occasion Heat ; with a comparative View of the Laws to which- 

 Light and Heat, or rather the Rays which occasion them, are 

 subject, in order to determine whether they are the same, or 

 different. By William Herschel, LL. D. F. R. S. p. 293 



XVI. Chemical Experiments on Zoophytes; with some Observa- 

 tions on the component Parts of Membrane. By Charles 

 Hatchett, Esq. F. R. S. - - - p. 327 



XVII. On the Electricity excited by the mere Contact of con- 

 ducting Substances of different kinds. In a Letter from Mr. 

 Alexander Volta, F. R. S. Professor of Natural Philosophy 



