468 



SCIENCE 



[Vol. LVI, Xo. 1452 



declination, the change in the earth's magnetic 

 field is in the direction tha:t would be produced 

 by the change in the earth-current intensity 

 and in the electric potential of the earth, hence 

 the current can not be caused by the variation 

 in the magnetic intensity. 



Both the earth-currents and the diurnal mag- 

 netic variations are in the direction which they 

 would take if they were caused by the electro- 

 static induction of the sun's negative charge, 

 while the permanent magnetic field of the earth 

 is such as would be caused by the rotation of its 

 own permanent negative charge. 



Figure 3 shows the relation between the ob- 

 served mean, diurnal variation of the earth-cur- 

 rent in a line about two miles long at Palo Alto 

 and the diurnal variation of the earth's poten- 

 tial for the same three days, as shown by the 

 photographic record. On account of the dis- 

 turbances in the earth due to trolley lines and 

 other causes, and to possible disturbances in the 

 line, which has been kindly put at my disposal 

 by the Pacific Telephone and Telegraph Com- 

 pany, it is impossible to record the earth-cur- 

 rents photographically with any instrument at 

 my command, and I have been compelled to 

 make all the observations visually. As I have 

 no assistance, I am compelled to make the con- 

 tinuous twenty-four hour runs myself, and for 

 this reason I have at the present time but three 

 such complete records, viz., for June 2, July 18 

 and August 10, of the present year. The mean 



diurnal variation for these three days is shown 

 in Cui-ve A in Figure 3, while the mean diuimal 

 variation in earth potential for the same three 

 days is shown by the dotted curve, B. In this 

 curve the signs of the potential are inverted to 

 show better the agreement of the two curves. 

 Both etirves show many irregularities which 

 would probably disappear in the mean of a 

 large number of observations, but their similar- 

 ity in general outline is such as to make it hard 

 to doubt that they are physically related. 

 Their time relation seems to indicate that the 

 positive charge on the day side of the earth is 

 due to the movement of electrons away from 

 the sun. 



Fernando Sanpoed 



Stanford University 



RESEARCH AT THE TORTUGAS 

 LABORATORY 



The untimely death of Alfred Goldsborough 

 Mayor and the consequent interruption of the 

 plans of the Tortugas Laboratory of the Car- 

 negie Institution of Washington naturally 

 arouses renewed interest in the work of the 

 laboratory and especially in the investigations 

 now being carried on there. It may therefore 

 be desirable to bring to general notice a brief 

 resume of the activities of the laboratory and 

 also to point out the purposes of some of the 

 researches now in progress. 



The laboratory has been in existence for 

 eighteen years and during that time it has 

 published seventeen large volumes of "Papers 

 from the Tortugas Laboi-atory," with one or 

 two volumes more in preparation.. In addi- 

 tion, a large number of papers, based in whole 

 or in part on work done at the laboratory, 

 were published elsewhere, one of the most im- 

 portant of these being Mayor's own work of 

 three volumes on the Medusre. (Fui-ther dis- 

 cussion of Mayor's researches is found in 

 Davenport's interesting paper in Science, 

 August 4, 1922). Among the contributors of 

 these papers are many of America's most pro- 

 ductive biologists. In estimating the produc- 

 tive activity of the laboratory it is necessary 

 to remember that the laboratory has been open 

 only from eight to fourteen weeks each year 

 and that the greater part of the work has been 



