Show HOW gravitation VARIES I 1 probably asins d by y S subterranean ate fanean commotions commotion that changes involving the displacement of immense masses are going on within the earth is one of the suggested explanations explanation of some observations recently announced in france it has been found at the pare st maur observatory that the force of gravitation or the we weight ight of bodies undergoes daily variations these are rendered sensible by placing in the earth a tube containing a column of mercury balanced by the pressure of hydrogen contained in a closed vessel connected with the tube and registering by means of photography the alterations in the lavel of the mercury after all corrections have been made for the effect of changes of temperature it appears that certain sudden variations in the level of the mercury are only to be explained on the theory that they are diieno due to changes in gravitation th these variations last from fifteen minutes to an hour they are of course course very small au amounting agutina utina at a maximum to one ane twentieth of a millimeter b but u t they may imply very great displacements of matter in the interior of the globe it has been suggested that similar experiments should be conducted in the neighborhood of active volcanoes where liquefied rock is moving beneath the surface and other disturbances of the strata of the earth are taking place such facts as these present to the imagination a very formidable picture of the gigantic commotions that accompany the slow cooling and con contraction trac of the globe on whose hardened crust we rear our edifices wondering when some efthem of them are occasionally shaken down by earthquakes at the instability of a planet that is apparently so solid |