174 



Marvels of the Universe 



Photo Jy] 



This 



[Russell F. (;irinni=lK 

 THUNDERBOLT.- 



fell in ^ orkshire 



stony meteorite 

 in 1861 



of climate were experienced within comparatively modern 

 times, when plants and animals were already largely of kinds 

 living at the present day in various parts of the world. 



Now, not only climate — that is, the general conditions 

 of temperature, rainfall and so on experienced throughout 

 all the seasons — but also the actual weather experienced on a 

 certain day may sometimes be traced in the rocks. These 

 may, for instance, record the occurrence on a certain day, 

 millions of years ago, of a short but sharp shower of rain, 

 succeeded by brilliant sunshine, with a south-east breeze 

 blowing rather strongly. In another case, a thunderstorm 

 takes place and lightning flashes through the sky. 



Such " Fossil ^^'EATHER " is here illustrated. In the first 

 picture, specimens A, C, E and F show the effect of a showery 

 day at the seaside. The rain must have been very brief, as 

 shown by the small number of rain-pittings on the mud or 

 fine sand of the beach ; sharp, also, because of the depth of 

 the pits. 



Specimen C is not the actual surface on which the shower 

 fell, but the later deposit of sand which was washed over it, 

 burying and preserving the rain-marks. It is thus a sort of " negative " or " cast," showing the 

 pittings as httle mounds, among which are ridges representing cracks due to the drying and 

 shrinking of the sandy beach in the great heat of the sunshine which succeeded the shower. 



In some cases the gi-eat depth of the pittings suggests that hail, instead of rain, produced them. 

 Specimen A was formed recently at Cromer, and the regular shape of the pits here, and in F (from the 

 Bay of Fundy), show that the rain fell straight down, so that evidently no wind was blowing. But 

 in the case of E, formed ages ago in Co. Down, in Ireland, the direction of the wind is unmistakably 



indicated by the fact that all the rain-pittings are deeper 

 on one side than on the other : the rain fell obliquely, driven 

 slantwise by a strong wind. The actual direction of that 

 ancient breeze is found by noting the position which the 

 slab of stone occupied in the sandstone quarry whence it 

 came. 



Permanent evidences of thunderstorms are rarer, though 

 occasionally a flash of lightning, striking a sandy surface, 

 will melt the grains, so that they run into one another and 

 form a hollow tube, or pipe, of glass-like material. Such 

 a " lightning-tube," from Starczynow, in Poland, is shown 

 by B in the photograph. One small piece of it is viewed 

 endwise, so as to show the central hollow. Much commoner 

 are the cigar-shaped objects shown in D, and popularly 

 known as " thunderbolts." These are hollow at one end 

 only, and pointed at the other, and have in reality nothing 

 whatever to do with thunder or any other condition of 

 weather. They are the stony internal guards of a sort of 

 ancient cuttlefish. 



The nearest approach to such a thing as a " thunder- 

 bolt " — in the sense of something fallen from the sky — is 

 a meteorite, or shooting-star But these may fall in any 



Photo Ja] IRiissell F. Gwiimell. 



A ■■THUNDERBOLT." 



An iron meteorite, weighing forty-four 

 pounds, that fell in India. Notice the surface 

 markings, a sure sign of the action of heat 



