208 



SCIENCE. 



[N. S. Vol. XVIII. No. 450. 



The experiments on kites at Blue Hill 

 have led me to the conclusion that the con- 

 ditions which confront the experimenter 

 are not so favorable as suggested by Pro- 

 fessor Bell, nor so hard as suggested by 

 Professor Newcomb. 



I made some experiments in 1898 with 

 a compound kite built up of a number of 

 small rectangular kites such as are called 

 the Blue Hill Naval Kites. In addition 

 to the necessity of giving greater space be- 

 tween the cells with increasing size, I 

 found two other difficulties: (1) When sev- 

 eral small kites are combined into one, the 

 pull of all the kites is concentrated on cer- 

 tain points which need to be strengthened 

 by using larger sticks. This may be partly 

 overcome by tying a string to each unit 

 and bringing the separate strings to a single 

 flying line at some distance from the kite. 

 But in such a case there is a crushing strain 

 on the central units due to ' the inward 

 pressure of the outer units, so that the kite 

 must be strengthened by trusses or larger 

 sticks if the compound kite is to fly through 

 the same range of wind-velocity as the unit. 

 (2) When a compound kite strikes the 

 ground the unit which first reaches the 

 ground has above it the combined weight 

 of all the other units and is instantly 

 . crushed in conditions where the unit flying 

 alone would not have been injured in the 

 slightest. ' This effect was so serious an ob- 

 jection that it led me to abandon the effort 

 to build a compound kite out of units. 



On the other hand, the weight of kites 

 built on the same model does not increase 

 so fast in practice as Professor Newcomb 's 

 law implies. The experience at Blue Hill 

 is that if one can build a kite four feet high 

 sufficiently strong for practical work, and 

 it weighs one and one half ounces per 

 square foot, then one can build a similar 

 kite eight feet high which will weigh two 



oimces per square foot and be siifficiently 

 strong for practical work. Mr. C. H. Lam- 

 son built a kite thirty feet high with two 

 cells similar to the kites used at Blue Hill, 

 and it weighed only about four oiinces per 

 square foot. This kite easily lifted a young 

 man weighing about 130 pounds into the 

 air, and, unloaded, flew beautifully in a 

 wind of fifteen to twenty miles an hour, 

 as witnessed by Mr. A. L. Rotch, Mr. S. 

 P. Fergusson and myself. 



The reason of this departure from Pro- 

 fessor Newcomb 's law is that only the 

 sticks of the kites increase in size (and the 

 necessity of this is usually partly overcome 

 by internal bracing), while the thickness 

 of the surfaces remains the same through 

 wide limits. 



But independent of these considerations. 

 Professor Bell's principle of tetrahedral 

 construction seems a promising one and 

 further experiments are awaited with much 

 interest, while the structure he has already 

 developed may be foimd of great use by 

 experimenters. 



H. H. Clayton. 



Blue Hill Observatory. 



SCIENTIFIC BOOKS. 

 The Role of Diifusion and Osmotic Pressure 

 in Plants. By Burton Edward Livingston, 

 of the Department of Botany. The Decen- 

 nial Publications, Second Series, Volume 

 VIII., Chicago. The University of Chi- 

 cago Press. 1902. 8vo. Pp. xiv -]- 150. 

 As stated in the preface : " The present 

 volume will deal with the past and present" 

 of diffusion and osmotic pressure from the 

 standpoint of plant physiology. It has a 

 double raison d'etre. First, it was felt that 

 there was need of some direct and not too 

 exhaustive account of the essential physical 

 facts and theories of the subject. The in- 

 terest of the physical chemist here has lain 

 mainly in the light which these phenomena 

 have been able to throw upon the ultimate 

 nature of matter and upon electrolytic proc- 



