70 NOTES ON THE 



sion of the sun's rays upon it vary, that the comet's 

 orbit is eccentric ? 



105. If those comets which circulate about the 

 sun in vast eccentric orbits are oceans isolated in 

 space, would the impact of a comet upon our world 

 be a force adequate to produce those phenomena 

 which are presented to us in the formation of the 

 boulder clay ? 



According to geologists, the boulder clay formation 

 appears to emanate from a common centre, and owes 

 its origin to no ordinary operations of water. It 

 consists of accumulations of sands, gravel, clays, and 

 boulder stones, huddled up in the same indiscriminate 

 mass, without regard to sedimentary deposition, or to 

 gravity, or to any other law of arrangement. 



] 06. When a comet approaches the sun, how is it 

 that the nebulous matter which constitutes the tail, 

 is extended in the wake of that body ; and how is 

 it when a comet recedes from the sun, the nebulous 

 matter which constituted the tail, is extended in 

 advance of the nucleus ? Is it from this cause : 

 Matter ceases not to be projected from the sun, the 

 momentum of which is such, that as it impinges 

 upon the nebulous atmosphere which surrounds the 

 nucleus of a comet, that atmosphere, during a comet's 

 approach to the sun, is impelled behind and beyond 



