468 Intelligence and Miscellaneous Articles. 



workmen, and that the different forms were intended to answer dif- 

 ferent purposes. At Brandon, implements formed of quartzite were 

 found in a bed consisting of rounded quartzite pebbles mixed with 

 about one-fourth of flints. Phut implements occurred beneath this 

 bed. 



The author indicated the geographical characters of the district 

 and the peculiarities in the distribution of the flint implements, which 

 he regarded as in accordance with the phenomena presented by the 

 valley of the Somme ; and he argued from the consideration of all the 

 facts that the implements were not transported to their present 

 situation by the agency of the rivers in whose valleys they occur, 

 but that they were made upon the spot, exposed upon the surface 

 with the gravels in which they are found and from which they were 

 made, and finally covered up by the river-gravels and sandy beds 

 which now overlie them. 



LVIII. Intelligence and Miscellaneous Articles. 



ON THE EXTENSION OF LIQUIDS UPON EACH OTHER. 

 BY R. LUDTGE. 



TX7HEN a drop of liquid is placed on the surface of another liquid 

 " ' with which it does not mix, either the drop may retain the shape 

 of a lens floating on this liquid, or it may spread out and form a very 

 thin layer. The first case is that of a drop of water placed upon oil. 

 or of a drop of oil upon alcohol ; the second that of oil upon water, 

 or of alcohol on glycerine. 



It is readily ascertained that the thickness of the liquid on which 

 is placed the drop of the second substance has an influence on the 

 extension of this drop on its surface. If this thickness is adequate 

 (at least 1 centim.), the drop readily expands, forming a very thin 

 layer, too thin indeed to produce the phenomenon of coloured rings. 

 When it is very small (1 to 5 millims. and even less), the drop in 

 extending hollows in its centre the liquid surface, to such an extent 

 sometimes as to moisten the bottom of the vessel in which the surface 

 was contained, by driving away at this point the liquid which origi- 

 nally covered it. The nature of the material of which the vessel is 

 made has no influence on the relative positions which the two liquids 

 assume under these circumstances ; it does not seem to depend on 

 any difference in the force with which the two liquids adhere to the 

 bottom. 



M. Ludtge brings this out more clearly by the following experiment, 

 in which he quite gets rid of the vessel, so that adhesion cannot 

 come into play. On a lamina of oil produced in a circular iron wire 

 frame, he places a drop of soap-water ; there is thus formed a circular 

 lamina of soap- water which gradually extends into the interior of the 

 lamina of oil until it fills the entire ring, while the oil is repelled in 

 the form of small droplets which adhere to the iron wire. A lamina 

 of water may also first be produced in the ring ; this may be driven 

 away by a drop of oil delicately placed upon it, which spreads 

 over the frame in its place ; and this lamina of oil may finally be re- 

 placed by another of soap-water, as we have seen. We might obvi- 



