Fertnanent Colours of Opake Bodies. 039 



mufl; be endued with a fmall degree of reflexive 

 power. Therefore, although they may be invi- 

 fible, when feparately viewed, yet when the 

 forces of a great number of fuch minute bodies 

 are united, their adtion on the rays of light be- 

 comes perceptible; fome forts of rays being re- 

 flected by them, whilft others are tranfmitted 

 through their intervals, according to the quan- 

 tity of refledive matter, which the rays arrive 

 at, in the internal parts of the water. 



The opacity of the fea, caufed by the nu- 

 merous reflexions from its internal parts is (6 

 confiderable, that extenfive mafles of it cannoc 

 be fecn through: even although the obftacle 

 arifing from the colourlefs light, reflefled from 

 its furface, be removed, by viewing the lower 

 part of the water, through a dark tube immerfed 

 under the furface, at the bottom of which a 

 polilhed glafs plate is joined. 



The nature and origin of the particles, which 

 diminilh the tranfparency of the water of the fea, 

 have not hitherto been examined, except as far 

 as relates to the more obvious faline, and earthy, 

 fubftances which are commonly obtained from 

 its analylis. 



Yet, although the matter, of which thefc 

 particles are formed, is not afcertained, it is cer- 

 tain that they are endued withafomevvhat greater 

 refledive power, than thofe which are fufpended 



in 



