October 5, 1900.] 



SCIENCE. 



523 



the air, the total pressure of the wind must 

 be very great and its tendency is always to 

 drive the wire and kites to a lower altitude. 

 Wind pressures of 30 to 50 kilograms per 

 square meter of surface exposed normally to 

 the wind are not uncommon, and it appears 

 that the line presenting the smallest surface, 

 relative to weight, is the one best to employ. 

 Considering the wire alone, there is an ad- 

 vantage in using the largest size of wire, 

 but there appears to be a practical limit to 

 the number of kites that may be efficiently 

 employed on one line. At Blue Hill, at 

 present, the average number of kites em- 

 ployed at one time is six — three large and 

 three small — having a total lifting surface of 

 less than 30 square meters. Since it is not 

 desirable to increase the size of the kites, 

 the increased power required to lift a larger 

 wire must be derived from a number of the 

 largest kites now used ; and since more than 

 eight kites can seldom be used to advantage, 

 it appears that a No. 25 or a No. 26 wire will 

 give the best results, until there can be ob- 

 tained better kites capable of lifting a larger 

 wire. It is also probable that a line made 

 up of several different sizes of wire may be 

 more efficient than one of uniform size. 



The present maximum height (4,850 me- 

 ters) in all probability is not the highest at- 

 tainable with No. 17 wire, and while it is 

 unsafe to predict the result of future ex- 

 periment, it now seems likely that, with a 

 stronger line and kites of greatest efficiency, 

 heights exceeding 6,000 meters are within 

 reach. Moreover, flights to elevations of 

 4,000 meters or higher could be made more 

 quickly and easily than at present. 



S. P. Fbrgtjsson. 



Blue Hill Obskrvatoey, 

 September 12, 1900. 



SCIENTIFIC BOOKS. 

 THE PUBLICATIONS OF THE VOLTA BXJEEAU. 



While the Volta Bureau was founded, by 

 Alexander Graham Bell, ' for the increase and 



diffusion of knowledge relating to the deaf,' 

 with a philanthropic desire to promote their 

 welfare, the publications of the bureau will in- 

 terest students in many departments of science, 

 and the purpose of this review is to call atten- 

 tion to some of the general bearings of two of 

 these publications. 



I. The Helen Keller Souvenir (2) Commemora- 

 ting the Harvard Final Examination for Ead- 

 cliflfe College, June, 1899. By A. Geaham 

 Bell, Annie M. Sullivan, and others. 

 It is less remarkable that Helen Keller, who 

 was born blind as well as deaf, has passed the 

 examinations for admission to Harvard Univer- 

 sity, ' with credit in advanced Latin': than that 

 she has become so familiar with the use of lan- 

 guage that she finds no more difficulty in the 

 work of the college class-room than any other 

 bright student. 



The way in which this result has been reached, 

 in the face of such difficulties, should be studied 

 by all teachers, not only for tbeir encourage- 

 ment, but because they will find in it an illus- 

 tration of the requisites which are essential for 

 all successful instruction. 



Her first teacher. Miss Sullivan, speaking of 

 her at the age of twelve, or thereabouts, says 

 that while her accomplishments seem marvelous 

 to many, they " consist only in her being able 

 to speak and write the language of her coun- 

 try with greater ease and fluency than the 

 average seeing and hearing child of her age." 

 Miss Sullivan asks whether we may not hope 

 for similar results with children who are so 

 fortunate as to have eyes and ears with which 

 to see and hear, and all who are familiar with 

 the lamentable failure of a common school edu- 

 cation to give command of the English language 

 must feel an interest in the answer. 



Helen Keller was not taught the use of lang- 

 uage. She was put into the way to discover its 

 meaning, and was left to make the discovery 

 for herself, as every normal child does, and 

 as we find out everything else that is worth 

 knowing. But while normal children make 

 this discovery at too early an age to be able to 

 tell us about it, Helen did not make it until 

 she had enough maturity of mind to reflect 

 upon it, and enough natural knowledge to know 

 her need of it, and to understand its value. 



