ATMOSPHERE 159 
TABLE XXXV 
SHOWING VARIATION OF SAND TEMPERATURE WITH DrprH AND MOoIsturE CONTENT: 
Arr 36° C. 
Dry Sand Moist Sand 
Da BiCils DELOWNBUTIACE sp bey otss se ss0n 0 eelnee HlypaNe? Ban. 
BeANSCIN WOELOMEBUTLACE an sislss sirais ole vo e's» 5 adel. Aon 1c Ch Op 
BOM CM DELOWABUILACE hiss cng reds cp eebcee nace ci (Oe 29° C, 
LO DUC DELON BULIACC Ns ios cr cvs ev enelvens 33. C. ue, warone 
D2 s CU) DELOWISULLACE ei. b 6.6 55 0s snd ences vee ne AGO a7, 
DTC DECLOW BULIACE is sve creer cceneccesers 20° (Gy Hy ea ante 
It will be noted from the table that temperature decreases with depth 
and with increasing moisture. 
4. PLANTS AND ANIMALS 
Cowles (120) mentions the importance of soil bacteria which increase 
with the increase of the humus, and the development of substances toxic 
to the plants producing them (121, 114a). Little is known of the effect of 
animals upon the soils in which they live but if excretory products ever 
accumulate in any quantity, they probably have a detrimental effect, 
especially upon the animals which produce them (114). On the other 
hand, many burrowing animals bury organic material and bring mineral 
soil to the surface. The digger wasps add much to the sand by burying 
many insects for their young. Earthworms contribute to soil forma- 
tion (30). Cowles states further on the authority of Transeau (122) that 
humus accumulation alters soil aeration. It follows that the atmosphere 
available to subterranean animals differs in different soils. 
III. ATMOSPHERE 
Animals living fully exposed to the atmosphere are usually those most 
dependent upon the various physical factors of the air, viz., light, 
temperature, pressure, humidity, currents, electrical conditions, ete. 
I. LIGHT 
Animals are either positive or negative to the actinic rays of the 
spectrum (45, 123). Considerable work has been done by plant 
ecologists, on the measurement of light with photographic papers, but its 
bearing on plant problems is questioned by some because the nonactinic 
portion of the spectrum is most important in the process of photosyn- 
thesis. It appears that these measurements are of much greater signifi- 
cance for animals than for plants. Zon and Graves (124) have brought 
