positions of what is called "biotopo>;raphy" or the forminj; of 

 land surfaces by animals, for he demonstrates that these thou 

 sands of square miles of mounds were all built by the small, 

 burrowinj; rodents called poc-ket gophers The method they use 

 in digginji; and the result this has on certain types of terrain 

 alone seem capable of producing these mounds. Dr. Scheffer 

 produces evidence that these animals had been at work 

 wherever such mounds are found, but he cautions that the exact 

 method of their construction has never yet been observed in 

 action— by pocket gophers or any other agency, biotic or physi- 

 cal. It seems, however, that in areas where the subsoil is very 

 firmly compacted or very rocky, or where the surface soil lies on 

 rock, these mounds appear. It is assumed that the animals bur- 

 row down as far as they can and throw the detritus up out of 

 their holes Then as they extend galleries radially underground, 

 they cause a hollow in the soil but a low dome above it, each 

 animal family working a limited area. Rain water then collects 

 in the gutters between these areas, while different plants grow 

 on the slopes of the mounds and on top of them; so that by 

 addition of soil on top and by washing away at the bottom, they 

 form these domes, which are on an average about six feet high 

 at the middle. 



FROM ALPS TO DESERTS 



These prairies are, as I mentioned above, ringed by a ribbon of 

 parkland, and this in turn closes up so that the trees form a 

 closed-canopy temperate woodland as you go up the sides of the 

 encircling mountains. Then, if you continue upward, the com- 

 position of this deciduous forest changes and the conifers begin 

 to appear, while the hardwoods thin out. Eventually one enters 

 the pure northern coniferous forest with all its belts (as seen at 

 sea level as one travels north) neatly arranged horizontally in 

 zones one above the other. On the higher peaks the spruces open 

 out just as they do at the southern edge of the Arctic tundra. 

 and true montane tundra appears in the form of tiny dwarf 

 willows, mosses, and all the rest, to form a zone that has been 

 locally called the "Hudsonian." Above this the tundra creeps 

 up near the peaks but finally gives way to true barren ground 

 with nothing but lichens. There is no better place in the world to 

 see for yourself the rigid zoning of vegetational types and the 

 invariable succession of these belts. Moreover, if you start your 

 ascent up the Sierra Nevada from the Sacramento valley near 

 its southern end, you will pass through all the major belts found 

 on this continent north of the Mexican border. 



Though this province is by no means the largest on the con- 

 tinent it is. apart from Mexico, by far the most varied. To de- 

 scribe it as a whole requires two separate expositions. First is 

 that of its "basis." whidi is to say its lowlands as they may be 

 seen today and as they would cover the whole of the area if the 

 mountain ranges were not present. Second, the mountain ranges 

 have to be described: but these are all so different that they 

 cannot be treated as a whole. The best procedure, therefore, is 

 to start at the north end of the coastal string, proceed south to 

 the San Bias, and then come back up the inland diain. This has 

 the added advantage of leading us back up to the appropriate 

 edge of the next province to be discussed. We may therefore 

 begin with the Olympic Peninsula. 



This, as we have seen, contains a central mountain range of 



A mule deer fawn pauses at the foot of a great Silka Spruce 

 in the upper montane forest of the Sierra Nevada. 



