## Abstract

The values of gravity at these stations have been compared by means of pendulum observations with Invar invariable pendulums. The observed differences of gravity from the National Physical Laboratory are: $ \matrix\format\l\kern.8em&\l \\ \text{B.I.P.M.} & -256\cdot 73\pm 0\cdot 49\,\text{mgal} \\ \text{P.T.B.} & +\ \,68\cdot 68\pm 0\cdot 49\,\text{mgal} \\ \text{Bad Harzburg} & -\ \,15\cdot 68\pm 0\cdot 49\,\text{mgal} \endmatrix $ The accuracy of the measurements is not so great as has been achieved once or twice previously with the same apparatus, mainly because the changes in the lengths of the pendulums were greater than usual. These differences have been combined with German pendulum observations and with gravimeter comparisons with the following results: Value of gravity at N.P.L. on the Potsdam system: 981196$\cdot $29 $\pm $ 0$\cdot $3 mgal. Differences between sites of absolute determinations of gravity: $\aligned \text{N.P.L.}-\text{B.I.P.M.}\quad +256\cdot 45\pm 0\cdot 3\,\text{mgal}\\ \text{N.P.L.}-\text{P.T.B.}\quad \quad -\ \,68\cdot 98\pm 0\cdot 3\,\text{mgal}\\ \text{P.T.B.}-\text{Potsdam}\quad -\ \ 8\cdot 95\pm \, 0\cdot 4\,\text{mgal}\\ (g\ \text{at Potsdam}=981274\,\text{mgal}.)\quad \quad \endaligned $ (g at Potsdam = 981274 mgal.) The effects of these results on gravity surveys based on Cambridge and on the absolute value of gravity are indicated.

## Royal Society Login

Sign in for Fellows of the Royal Society

Fellows: please access the online journals via the Fellows’ Room

### Log in using your username and password

### Log in through your institution

Pay Per Article - You may access this article or this issue (from the computer you are currently using) for 30 days.

Regain Access - You can regain access to a recent Pay per Article or Pay per Issue purchase if your access period has not yet expired.