ECOLOGY. 409 



rapidity of this process have been increased b}'- sifting the soil in a 

 very thin layer over white oilcloth niled in squares and by using a 

 binocular magnifier to disclose the larger organisms. 



A new model of the apparatus described by Holdhaus has been 

 constructed. This consists of three 12-inch water- jacketed copper 

 funnels with asbestos covering, each of which is connected with a 

 central tank in which the water is kept warm by means of an alcohol 

 blast-lamp. Actual tests of the efficiency of the apparatus have been 

 made at various temperatures and with different organisms by plac- 

 ing a known number in a sample of soil and determining the percent- 

 age separated by it. In addition to the water-content, organic 

 matter, mechanical composition, and temperature, the volume and 

 composition of the soil atmosphere and the acidity are being deter- 

 mined for each habitat. It is also planned to make quantitative 

 studies of the algae and molds of the soil in the hope of getting at the 

 reactions concerned. 



Climatic Cycles, by F. E. Clements and A. E. Douglass. 



In continuing the investigation of climatic cycles by means of the 

 annual rings of trees, sections have been collected from the redwood 

 at Santa Cruz, California, from pines in the Santa Rita Mountains 

 of Arizona, and from the white pine in eastern Massachusetts. In 

 addition, material was obtained from a group of buried pines at 

 Flagstaff, Arizona, fragments of buried sequoia from Oroville, and a 

 piece of wood, perhaps cypress, from the Rancho La Brea, near Los 

 Angeles. A plotting micrometer has been constructed for the measure- 

 ment of tree-rings with automatic plotting, thus rendering the process 

 of measurement much more rapid. A general reduction has been 

 made of 3,000-year sequoia records from 35 trees to secure the best 

 standardized curve, and the same has been repeated in decade sums 

 to obtain longer periods A final cutting has likewise been made for 

 the analysis of some thirty 500-year sequoia curves for tests of topog- 

 raphy and growth. 



The prelimina'-y analysis of the cyclic nature of rainfall in the 

 western United States has not only shown that critical drought 

 periods since 1835 have coincided with sun-spot maxima, but also 

 that such periods have always occurred when maxima reach a certain 

 degree of intensitj^ The rainfall of the West is now being analyzed 

 with reference to a possible relation between wet periods and sun- 

 spot minima, and to the relation of temperature to rainfall and to 

 sun-spot numbers. In addition, the rainfall at certain stations and 

 in certain regions appears to have a complementary relation to other 

 stations or regions, and it is hoped that the examination of the records 

 of the thousand or more stations concerned will afford some expla- 

 nation of this. 



