August 16, 1907] 



SCIENCE 



221 



had been previously healthy in every re- 

 spect. 



The various species of Pestalozzia have 

 been known as parasites in Europe, causing 

 disease of conifers of one to several years' age. 

 The same fungus was found in 1903 in Texas 

 and also upon young pine trees from North 

 Carolina and New York in 1906 by the writer. 

 There can be little doubt that it occurs gen- 

 erally in the United States, and sometimes at 

 least, as a true parasite. The fact that it 

 occurs as a parasite upon young conifers seems 

 not to have been proved in this country by 

 other workers. The present article may be 

 taken as a warning to managers of conifer 

 nurseries, as it is more than likely that similar 

 outbreaks of this disease will be noted in the 

 near future. Eemoving the diseased trees 

 and burning them, accompanied by thorough 

 spraying of the remainder with Bordeaux mix- 

 ture containing some adhesive substance to 

 make it cover the smooth needles, should com- 

 pletely control the trouble and stop its spread 

 into unaffected seed beds. 



Peeley Spauldino 



Bureau op Plant Industry, 

 U. S. Department of Agriculture 



normal faulting in the bullfrog district 

 The Bullfrog Mining District is situated in 

 southern Nevada, about ten miles from the 

 California line, and sixty miles south-south- 

 east of Goldfield. The towns within the dis- 

 trict are Ehyolite, Beatty and Bullfrog. In 

 1906 Mr. G. H. Garrey and the speaker 

 mapped the general geology of a strip across 

 the district, seven miles long and three miles 

 wide. The country is a desert, the rocks are 

 bare and exposures are exceptionally good. 

 The relief is about 2,500 feet. Mining ex- 

 ploration has added greatly to the natural 

 exposures, and conditions for field work are 

 unusual. 



The oldest rocks form a crystalline complex, 

 consisting in the main of quartz-biotite 

 schists, quartzites, limestone, pegmatite, in- 

 jection schists and gneisses, which surround 

 small areas of sheared diorites. This com- 

 plex is the equivalent of a series of sedi- 

 mentary rocks which has been greatly meta- 



morphosed. Above the schists is a massive 

 limestone, about 100 feet thick, probably 

 Silurian. In faulted contact with the lime- 

 stone and older rocks is a great series of Ter- 

 tiary lava flows with subordinate beds of sedi- 

 mentary tuffs, limestone and shale, altogether 

 about Y,000 feet thick. Of the lava flows 

 there are sixteen separable divisions of rhyo- 

 lite, five basalt flows, one flow of dacite, and 

 one of quartz basalt. Stratified tuffs of sedi- 

 mentary origin occur at two horizons, with 

 numerous lava flows between. The Tertiary 

 rocks are approximately conformable one with 

 another in dip, though there are slight 

 erosional unconformities at several places. 

 Basalt dikes, most of which are along fault 

 fissures, cut the older lavas. There was much 

 faulting after the dikes were intruded, and 

 the rhyolite-basalt contacts afforded planes of 

 weakness which were taken advantage of in 

 nearly every instance. Dikes and other in- 

 trusive masses of rhyolite also cut the lavas. 

 At three places there are small outcrops of 

 leucite basanite. 



The bedded rocks dip eastward at angles 

 averaging 27° and are traversed by faults, 

 most of which strike northeast and dip west. 

 Most of the faults are nearly perpendicular to 

 the beds and all are normal, that is, the 

 down-throw appears to have been down the dip 

 of fault planes and consequently the west 

 block is, in most cases, depressed, or the block 

 east of the fault plane is elevated with re- 

 spect to the down-thrown or hanging-wall side. 

 Since the dip of the beds is to the east and 

 the dip of the faults to the west, the same 

 beds occur repeatedly. Before deformation 

 the beds were approximately horizontal. In 

 the deformation two processes operated; fault- 

 ing, which tended to lower the beds to the 

 west or raise them to the east; and mono- 

 elinal folding or tilting, which tended to 

 raise the beds towards the west or lower them 

 to the east. A seven-mile east and west sec- 

 tion across the area shows that the eastward 

 depression due to tilting is 12,400 feet, which 

 is only 1,300 feet more than the westward 

 depression due to faulting, or that the result 

 of both processes was to leave the beds at 

 about the same elevation at the east and at 



