890 



SCIENCE. 



[N. S. Vol. XII. No. 310. 



strain which would suffice to account for gravi- 

 tation. But the outstanding difficulty would 

 be to explain the high velocity of propagation 

 of gravitation which seems to be required by 

 the known behavior of the solar system under 

 the action of the sun's gavitation. 



Of course it may be that the failure of the 

 linear relation between ether stress (electric 

 field) and ether strain is associated with ether 

 compression, and it might be possible to explain 

 in this way the high velocity of the propagation 

 of gravitation. The point, however, which we 

 wish to emphasize is that mere ether compres- 

 sion alone is not sufficient to explain gravita- 

 tion ; at least the compressional energy must 

 not be proportional simply to the square of the 

 resultant field intensity, for in this case the 

 compressional energy would not be distinguish- 

 able from the distortional energy which gives 

 rise to the ordinary electric attraction and re- 

 pulsion. If, however, the compressional energy 

 were proportional to the fourth power of the 

 resultant field intensity, then the ether com- 

 pression would not stand in a linear relation to 

 electric field intensity (ether stress), and the 

 above remarks concerning excess of the electric 

 attraction over repulsion would apply and grav- 

 itation would be provisionally explained. 



W. 8. Franklin. 



THE HOMING INSTINCT OF A TUETLE. 



To THE Editor of Science : The follow- 

 ing account from a friend, Miss Victoria Hay- 

 ward, of Bermuda, may be of interest to your 

 readers. I can vouch for the accuracy of the 

 relater, and know from experience that the 

 locating of an area on the reefs is as easy to a 

 Bermudan as if it were on dry land. Miss 

 Hayward writes : 



" My father caught a turtle in June that 

 weighed seventy-five pounds. He placed it in 

 a pond in the harbor of St. George. In August 

 on going to the pond he found that some person 

 had thrown a piece of iron weighing about fifty 

 pounds into the pond and it had broken a large 

 hole in the turtle's back. It had been wounded 

 apparently about a week and was weak and 

 seemingly dead. My father thought he had 

 better kill it, but he changed his mind, and let 

 it go alive into the harbor. 



' ' In the latter part of October he and another 

 man recaptured it in the same place where they 

 had caught it before — about four miles from 

 land, on the flats (reefs) that lie to the north of 

 the islands. The back was nicely healed and 

 the turtle was altogether in excellent condition. 

 You know that it requires no little knowledge 

 of the art of navigation for a turtle to find the 

 way from the southern side of St. George's 

 Harbor through some one of the many little 

 channels to its own special home on the north 

 reefs — four miles out to sea." 



C. L. Bristol. 



BOTANICAL NOTES. 

 PEACH LEAF CURL. 



According to a bulletin (No. 20) prepared 

 by N. B. Pierce and recently issued by the Di- 

 vision of Vegetable Physiology and Pathology 

 of the United States Department of Agricul- 

 ture, this disease appears to exist wherever the 

 peach is grown. It is known to occur in 

 North America, South America, Europe, South 

 Africa, New Zealand, Australia, Japan and 

 China. It is due to the presence of a minute 

 parasitic fungus — Exoascu.i deformans — one of 

 the simpler of the sac fungi — (Ascomyceteae). 

 The fungus attacks the parenchyma of the 

 leaves and twigs, enlarging, thickening, curl- 

 ing and distorting them. Eventually the 

 leaves become yellowish and fall off, involving 

 as a consequence the wilting and dropping of 

 the fruit. It has been estimated that the an- 

 nual loss in the United States from this source 

 alone amounts to between two and three mil- 

 lions of dollars. 



Mr. Pierce's paper discusses not only the 

 structure of the fungus and the nature of the 

 disease, but includes records of the many ex- 

 periments which he made in order to deter- 

 mine what are the most efficient means for 

 preventing or combating the disease in the or- 

 chard. He recommends spraying with Bor- 

 deaux Mixture of the following proportions ; 

 Copper sulphate, five pounds ; lime, five 

 pounds; water, forty- five gallons ; applying it 

 with what is known as a ' Cyclone Nozzle,' 

 and doing the work from one to three weeks 

 before the opening of the blossoms in the 

 spring. 



