23 LA EE — CIIELONIAN SCUTES FHOM THE STONESFIELD SLATE. 183 



than in the intervening periods. Now Tyndall speaks of the earth 

 receiving but the ^o ooVotttto P ar ^ °f the solar rays, and therefore it 

 might be said that the falling in of the earth would only reduce the 

 temperature of the earth by that part of a degree ; but, on the other 

 hand, we should have to consider what influence such an event would 

 produce if the point of collision and obscuration was in a direct line 

 with the earth. In such a case the direct light- and heat-rays would 

 be shut off, and although compensated for in a great degree by the con- 

 vergence of the surrounding rays in the great flood of light coming 

 away from the sun, a considerable eflect might be produced on the 

 temperature of the earth. Of what eflect might be produced we have 

 perhaps some examples in the actual effects produced by sun-spots. 

 Single spots often appear of dimensions equal to and exceeding that of 

 our earth, and periodically we have numerous congeries of spots of 

 sufficient importance to produce disturbances at any rate of the mag- 

 netical conditions of our globe if not indeed to produce any distinctly 

 perceptible diminution of temperature. That the latter effect might 

 not be readily determinable in the converging or fluctuating states by 

 our atmosphere is by no means surprising ; but it should be borne in 

 mind that Arago and other astronomers have asserted and attempted 

 to prove that the maximum periods of sun-spots are regular decades 

 of colder years. Such minute changes as those produced by these 

 minor differences in the amount of materials in actual conflagration 

 would have had little effect on the general climatal temperature of 

 our earth, but if a difference, no matter how small, could in this or 

 any other way be proved, it would be a basis for real conclusions on 

 the subject. There are, however, five other ways in which the solar 

 rays might affect the general climatal conditions of the earth. 1. The 

 mass of the sun being larger or smaller would radiate more or less 

 heat accordingly. 2. There might be maximum and minimum periods 

 of conflagration. 3. The extent of the earth's atmosphere might influ- 

 ence climatal condition by the conversion by friction of the light rays 

 into heat, just as light rays falling on a black surface are arrested, 

 annihilated, converted into heat, which they are, and on the same 

 principle that a falling bullet striking the ground has its velocity or 

 motion changed into an equivalent of heat. 4. A former higher and 

 lower rate of rotation of our own globe would have important effects 

 upon the climatal conditions and on the vegetation and life of our 

 planet. 5. Variations in the dimensions of the orbit of the earth. 



(To be continued.) 



ON CHELONIAN SCUTES FROM Till" ST OX ES El ELD 



SLATE. 



By C. Cabteb Blake, Esq. 



In the British Museum there are several specimens of " papiliona- 

 ceous" flattened bodies exhibiting six or more concentric lines ra- 



