tables of corrections wcrc avnilable wliich hnd becn worlted ont in the JIctroIogy Department. In the original of this nomograni the lcngtli OS was taken as 630 mm. and SP as 120 nim., wit11 ))I = 1 and ?I = 50 : the value of gravity at Teddington-being 981.195 cm./ scc.2, thc constnnt G has here tho voluc 0.530/980.665 = 0.000540. It has sincc becn recogniscd that the correct method would bc to make PQ sliglitly curved, in which case not only the tlicoreticiil error hiit also that involved in the tedious double projection may be svoided. If the snnie scales are used for B, rind A as liefore, the position and graduntion of the temperature scnlc PQ nrc foulid by n simple nomographic method using determinants* whicli gives
a)t/(l + Pt), 6 ' = 0*000540, 7 6 0 ~ = V(py ) t / d , ant1 a, (3, y hnvc the vnlues previously assigned to them.
I n an ordinary nnnlytical laboratory tlierc are very few occasions on which i t is necessary to know thc barometric pressurc more nccurately tlian to hO.05 mm. The nomogram illustratcd has thereforc been framed and affixed to the wall alongside the bnromctcr: i t is normally read through a glass front oti nhieh a celluloid strip with index line is lnid ; under these coiiditions thc correction can bc rend to about &0.01 mm. The authors acknow.ledgc nssistniicc and udvicc from Bfr. F. A. Gould of the Metrology Department in the preparation of this notc, which is published by permission of the Director, Nationnl Physical Laboratory. Seo I'cddle, " Conetruction of Crnphicnl Chnrta." AIcGraa-Hill Book Co., N e w York, 1010. neccivd hprii I, ~U I I ADSORPTION OF SATURATED LIGHT HYDRO-CARBONS BY ACTIVATED CHARCOALS By B. CRAWLEY Tho ndsorption of n series of chcniicnlly rclntetl pirro hydrocnrboirs (pnmflins, cyclopnrnfins, ntrrl nromntics) on ; ! r e 0 speoirncns of nctivntcd chnrcoda lrns becn studied. l h o results tlirow sonio light on tho odaorptivo clinrnctcristics of ilifferciit types of chnrconl.