166 ANNUAL OF SCIENTIFIC DISCOVERY. 



extremely small ; whereas, on the 28th instant, at three-quarters past 

 eleven A. M., in a heavy shower, only ninety-four millions of drops fell 

 per hectare in the course of a minute, the drops then being very 

 large. 



THE COHESION FIGURES OF LIQUIDS. 



This is a term applied by Mr. Charles Tomlinson, in the Philosophi- 

 cal Magazine, to the beautifully varied figures formed on the surface 

 of water, mercury, etc., by oil of lavender, creosote, or other liquids 

 dropped thereon. When one liquid is added to another and solution 

 takes place between them, there is always a breaking up of the cohe- 

 sion of one or other liquid ; where there is no solution there may be 

 simply adhesion. In both cases one liquid exhibits the characteristic 

 phenomena of cohesion. The essential oils are but slightly soluble in 

 water. If we place a drop of oil of lavender on the surface of the 

 water, the adhesion of the water will cause it to spread out into a film ; 

 but the cohesion of the oil immediately begins to reassert itself, the 

 film opens in a number of places, forming long irregular arms of pro- 

 cesses resembling the pattern assumed by wood when it has been 

 much worm-eaten. These processes tend to gather up into separate 

 disks or tentacules ; the adhesion of the water spreads them out ; the 

 cohesion of the oil struggles to prevent this, and soon prevails ; the 

 almost immediate issue being the formation of the original drop into 

 a number of disks with sharp, well defined outlines and convex sur- 

 faces. The action often is so rapid and the pattern so complicated, 

 that it requires repeated observation to become master -of all the 

 phenomena which are represented in a plate. Mr. Tomlinson con- 

 siders this to be the resultant of the cohesive force of the substance, 

 its density, and the adhesion of the surface on which it is placed, and 

 believes that every independent liquid has its own cohesion figure. 

 He gives a detailed' account of his experiments with creosote, carbolic 

 acid, ether, oil of cloves, olive oil, etc. He also suggests a mode of 

 applying these cohesion figures in detecting adulterations. Chemi- 

 cally pure water should be used as the recipient. If mercury be sub- 

 stituted new figures are obtained from the same liquid. 



THE BATHOMETER. 



At the last meeting of the British Association, 1861, Mr. C. W. 

 Siemens described an instrument, under the above name, designed to 

 indicate the depth of the sea without submerging a line. The sea- 

 water being considerably less in density than the rocks which consti- 

 tute the crust of the earth, Mr. Siemens showed, by considerations 

 derived from the integrals expressing the attractive force of any shell 

 of the crust of the earth, that the depth of water under a ship must 

 vary the total attractive force of the earth to such an amount as would 

 become sensible to a very sensitive instrument. He, therefore, devised 

 one, consisting of a body of air inclosed in a strong glass cylinder, made 

 to support, by its elasticity, a column of mercury contained in a tube 

 open at the bottom and dipping into it, kept at a uniform temperature 

 by being surrounded by melting ice. The tube containing the mer- 

 cury ends in a ball above, from winch rises another tube and ball, the 



