has been opened to it by the exlernal addition of' a germ crystal. 
The genn. crystal is not the cause of’ the reaction because it does 
not provide for the f'ree energy necessary for the process, bul is 
only the means of starting the process which goes to completion 
by its own f'orces af'ter it has been once begun. 
Now in a saturated solution of a substance there is equilibrium 
between the solution and the solid phase of that substance only ; 
in a supersaturated solution there is an excess of the dissolved sub- 
stance. Hence it seems reasonable that only the same solid phase 
should release its state of supersaturation ; consequently it seems 
improbable from theoretical considerations that an isomorphous sub- 
stance with which the solution is not in equilibrium would be able 
to release its state of supersaturation and this is corroborated by 
experimental observations. 
From this investigation it is clear that isomorphous substances or 
substances capable of forming solid Solutions are not able to release 
the state of supersaturation of substances with which this work was 
undertaken and hence considerable doubt is thrown on this test of 
isomorphism long advocated by numerous workers. 
In order to test the hypothesis more thoroughly, works in non- 
aqueous solvents with various solutes are in progress. 
Presidency College, Calcutta. 
fmperial College of Science , London. 
Scheikunde. — De Heer Ernst Cohen biedt eene mededeeling aan 
van den Heer Nilratan Dhar: „On Catalysis” . (Part II). 
(Zal in een volgend Zittingsverslag worden opgenomen). 
Geologie. — De Heer MolengrAaff biedt eene mededeeling aan 
van den Heer H. A. Brouwer: „Over de tektoniek der ooste- 
lijke Molukken.” 
(Mede aangeboden door den Heer Martin). 
Tijdens geologische verkenningstochten, welke door mij in dit 
jaar op verschillende eilanden der Molukken werden uitgevoerd 1 ), 
werden talrijke gegevens verkregen, die van belang zijn voor de 
tektoniek van het bereisde gebied. Waar het omvangrijke gesteenten- 
en fossielenmateriaal nog in het geheel niet is bewerkt, is het niet 
mijne bedoeling deze gegevens reeds thans in bijzonderheden te 
1 t Vgl. Voorloopige reisberichten in het Tijdschr. v. h. Kon. Ned. Aardr. Gen. 
1915 nos. 4 en vgl. 
