11X H'ljhry of AJlronomy for the Year \Z:)l, 



fraftion of prifms or of lenses, or by thin plates of air or 

 water between lenses made to approach each other, or by 

 the rinirs on bubbles, or by reflections or inflexions of light, 

 niav be explained from the fails contained in the above pro- 

 pofition. 



All the experiments, obfervations, and reafoning above, 

 refpeft onlv coloured Ugh'. I dare not venture, on theory, 

 to iiiVayi any tbing as to the exiftcnce of an elementary, pure, 

 uncoloured, uncompoundcd white light; yet that fome fuch 

 clemcntarv fubftance exifts, combined with one or more of 

 the principles of our atmol'phere, and alfo in combuftible 

 and inconibultible, and perhaps animal and vegetable iub- 

 Itanccs, feems to be probable ; for it can be feparated trom 

 fuch in various operations of nature and art. 



However, although ligbt may principally exifl:, combined 

 with caloric and other fubltanccs, in a gafeous form, yet it 

 may, and it is very generally admitted, that it does alfo exift, 

 independent of caloric, in folid bodies and fluids of various 

 kinds; and heat, it cannot be denied, exifts fenfibly in both 

 combuftible and incombuflible bodies which exhibit no vi- 

 fible light. Indeed, that light and heat are two diftinft exift- 

 ing principles is now finally and demonftrably afcertained and 

 proved bv Dr. Herfchel's curious experiments of the fa6l, 

 ihowing that heat as well as light are each liable to different 

 and peculiar rcfraftions, by which they are feparated from 

 each other, and take a feparate and diltintSl exillence in dif- 

 ferent fpace. 



Quod rcftat duhderatum eft. 



XXIII. Htftory of AJlronomy for the Year i8oi. By 

 Jekome Lalande. 



JL H E commencement of the 19th century was diftin- 

 guilhcd by an aftronomical event, the difcovery of a planet 

 at Palermo in Sicily, by M. Piazzi, on the itt of January*. 

 It was as fniall as a ftar of the 8th magnitude : he obferved 

 it during forty days. The obfervations he fent me arrived 

 too late for us to be able to follow it, and we were obliged to 

 calculate its orbit from his own obfervations alone. Burck- 

 hardt, Olbers, I ode, Piazzi, and Gaufs, have found that 

 to reprelcnt ihcfe obfervations it is necelTary to fuppofe that 



* 1 here employ the calendar of all nations, being perfuadcd that the 

 French woveininent \^ ill foun renounce the new calendar, which is not 

 underftood, and cannot be adopted either by our neighbours or by the 

 majority uf the French tliuinfelves. — L. 



it 



