30 Meteorites and What they Teach us. — Hensoldt. 
ice covered with metalliferous dust and other particles which 
were doubtless of cosmic origin, as they were found in regions 
far from the habitations of man and were unlike anything 
that could have been transported there by atmospheric or other 
agencies from a terrestrial source ; and no matter where he ex- 
amined snow, whether in Greenland, Spitzbergen, or the fro- 
zen coast of Siberia or in his own native Sweden, he never col- 
lected less than a millegrammein weight of meteoric particles 
from a square yard of surface. In one region, for instance, 
on his Vega expedition he found the snow covered for miles 
in extent with minute and very perfect crystals of yellowish 
color, like crystalized sand-grains. They were about 1 mm. 
in diameter and seemed to belong to the rhombic system, as 
they had one perfect cleavage and formed striated prisms, 
terminated at either end by a truncated pyramid. 
Now one millegramme to every square yard of the earth's 
surface, which is probably far below the annual fall of meteoric 
dust-particles, amounts for the whole globe to no less than five 
hundred million kilograms — about half a million tons — too 
important a factor to be neglected when the fundamental facts 
of the geological history of our planet are enumerated. That 
small quantities of cosmic dust, containing iron, nickel, cobalt, 
carbonaceous substances and phosphorus, constantly fall, with 
other atmospheric precipitates, on the earth's surface is a 
well established fact and there is even ground for believing that 
this deposit may play an important part in the economy of 
nature in supplying phosphorus to soils alread}' exhausted 
by the growth of crops. Farmers have long been taught by ex- 
perience that an exhausted field, if left unfilled for a number 
of years, will regain its fertility in proportion to the length of 
time during Avhich it remained fallow. 
The earth, travelling in its orbit around the sun, and onwards 
with the entire solar system around some unknown and still 
greater center of attraction, is constantly traversing new regions 
of space, which it depletes of meteoric dust and meteorites, 
thus steadil}^ — no matter how slowly — increasing in diameter. 
Now let this growth continue till the earth has just twice the 
attractive power which it now possesses ; we should then have 
twice the number of meteorites and double the quantity of dust 
falling annually upon it than now. Fortunately for our heads 
the earth has not as yet attained verv formidable dimensions, 
