ADVISORY committe;e on geophysics 67 



I do not think we yet know sufficiently how far neighboring 

 instruments give consistent readings even to the horizontal plane, 

 still less the nature of the differences in the vertical line. There is 

 always a doubt as to the proportion of the observed deflections 

 which are due to mere local warping of ths soil and building. For 

 example, it seemed useless for my brother and me to go on with our 

 pendulum observations here, when a large part of what we noted 

 was probably merely due to variations of water level in the river 

 gravel. Consistent readings from two instruments several miles 

 apart on the chalk hills would have had a very scientific value. 



If, however, we wish for example to study changes in the vertical, 

 to prove the existence or nonexistence of tremors due let me say to 

 distant volcanic explosions, etc., we require platforms not affected 

 by changes in temperature, underground moisture, and beyond the 

 range of artificially produced vibrations. Stations complying with 

 conditions such as these are rare. But would it be wise to build and 

 equip an institution in a proper locality before preliminary investi- 

 gations showed the realty of the phenomena to be investigated ? 



Then, again, there are so many researches where Mahomet must 

 go to the mountain . Take our seismic survey : With my stable as 

 a laboratory and the co-operation of thirty-six stations distributed 

 over the world, you know the results we are obtaining respecting 

 the physical nature of our planet, the districts which are yielding in 

 its crust, etc. Strassburg with its Government support and a labor- 

 atory I envy, is without this outside co-operation, with the result 

 that it can do but little more than publish its own registers. 



Again , if we wish to make observations on seismic disturbances 

 or changes in the vertical underground, we are again outside our 

 four walls. To measure the effects of tidal loads on coast lines — 

 the effects of barometrical pressures — secular deformations in the 

 crust of the earth — the variations in magnetic elements, or changes 

 in g\ say in the vicinity of extinct volcanoes, we may be i ,000 miles 

 away from our laboratory. And so I might continue suggesting 

 lines of research, none of which could be carried out in a particular 

 building. To my mind, what is required is a trust for geophysical 

 work. If the funds admit, let there be a central office laboratory 

 and staff, but the chief expenditures should be for investigation, 

 carried out in suitable localities or at existing establishments. * * * 



The enclosed pamphlets will show Mr. Walcott what I do during 

 the year. In addition there is a heavy correspondence with stations 

 and the instructors at Shide to be looked after. 



This work costs about ^150 a year * * * ." 



