836 



SCIENCE 



[N. S. Vol. XXIX. No. 751 



Of the whole bird population of the garden, only 

 four species are permanent residents. And these 

 are the bob-white, flicker, mockingbird and red- 

 bird. The regular visitors are the sparrow-hawk, 

 king-fisher, night-hawk, humming-bird, purple- 

 martin and cedar waxwing. The numerous hedges 

 of dense shrubbery harbor Bell's vireo, yellow 

 warbler, Maryland yellow-throat, chat, Traill's fly- 

 catcher and the indigo bunting. In the arboretum 

 are found the crested flycatcher, wood pewee, wood 

 thrush, cuckoos and the gentle mourning doves. 

 The meadow has attracted quails and meadow- 

 larks. The ripening mulberries are an attraction 

 for flocks of cedar birds in early June, and the 

 many beautiful flowers charm numberless hum- 

 mingbirds later in the summer. 



Thirty or more species of birds were on exhibi- 

 tion to illustrate Mr. Widmann's paper. 



At this meeting the following resolution was 

 adopted: "On the recommendation of its ento- 

 mological section, and with approval of its council, 

 the Academy of Science of St. Louis, on duly 

 seconded and passed motion at its regular meeting 

 of the fifteenth of March, 1909, respectfully urges 

 on the members of the General Assembly of the 

 State of Missouri, the importance of passing 

 House Bill No. 575, and Senate Bill No. 197, 

 providing the adequate inspection of nursery 

 stock. At the present moment the entire orchard 

 and nursery industry of the state is imperiled by 

 a threatened introduction of the dreaded brown- 

 tail moth, in the bare restriction of which New 

 England has for years waged a costly warfare. 

 Nothing but adequately planned and eSiciently 

 administered state inspection can protect this 

 important industry of Missouri in the present or 

 in future crises." 



On April 5, the Academy of Science of St. Louis 

 met to hear a paper presented by Prof. Whinthrop 

 Holt Chenery, of 'W^ashington University, on " The 

 lielation of the Physiography of the Iberian Penin- 

 sula to the Development of the Spanish and Portu- 

 guese Peoples." Mr. Chenery considered the 

 distinguishing features of the peninsula — topo- 

 graphic, geological and climatic — and their signi- 

 ficance as determining factors in the historical 

 evolution of the peoples. In particular he showed 

 that the chief occupations of the inhabitants, ever 

 since prehistoric times, have been determined by 

 the physical character of the country; and that 

 the long-continued prevalence of these occupations 

 has produced widely divergent types of people. 



The lecture was fully illustrated, and insistence 

 was laid upon the importance of the study of 



physical environment to the understanding of the 



Spanish-Portuguese history. 



W. E. McCouBT, 

 Recording Secretary 



THE PHILOSOPHICAI, SOCIETY OF WASHINGTON 



The 664th meeting was held April 10, 1909, 

 Vice-President Wead in the chair. Two papers 

 were read. 



Am Approximate Method of Analysis of E.M.F. 



Waves: P. C. Agnew. 



A knowledge of the impurities present in the 

 E.M.F. wave given by a generator is required in 

 many engineering and physical problems. While 

 a large number of methods have been devised for 

 the analysis of such E.M.F. waves, those methods 

 which give quantitative results require highly 

 specialized and expensive apparatus. The experi- 

 ments described were undertaken to determine if 

 it is possible to obtain reliable results by the use 

 of condensers and portable indicating instruments 

 only. 



For the same effective voltage, a distorted wave 

 will pass more current into a condenser than will 

 a pure sine wave. We ought, then, to be able to 

 use this fact to determine the amount of impuri- 

 ties present in a given wave. Obviously a greater 

 accuracy can be attained if we make the analysis 

 depend on bridge values of resistance, inductance 

 and capacity, and so make it independent of the 

 absolute calibrations of the voltmeter and amme- 

 ter used. This may be accomplished by replacing 

 the condenser by a resistance and adjusting to 

 give the same readings of ammeter and voltmeter. 

 We may consider that each component of voltage, 

 e,i, causes the corresponding component of cur- 

 rent, i„, to flow. The square of the effective value 

 of current indicated by the ammeter is equal to 

 the sum of the squares of the components. If in 

 the case of the presence of the wth harmonic only, 

 C represents the capacity, L the inductance, r the 

 resistance, and if p is 27r times the frequency, 





»^+ (pL-l/pC) 



+ - 



en' 



+ (npL — l/npC}-. 



Now on removing the condenser and increasing 

 the resistance to R, we have, for the same read- 

 ings of voltmeter and ammeter. 



r-= 



r= + 



ij2 -I- p=L- ^ R- + n-p'L- 



From these relations we get the ratio of the 

 harmonic to the fundamental E.M.F., 



