112 Mr. C. Tomlinson on the Action of 



One of my first experiments, made with the view to ascertain 

 what takes place when ether is brought into contact witli water, was 

 the following : — A goblet being quite tilled with water was placed 

 in a good light, and the finger well wetted with ether was brought 

 down very near the surface. On looking along this surface in 

 the direction of the light, a cup-shaped depression was evident. 

 I then dusted the surface of the water with a light powder, such 

 as lycopodium, and on presenting the finger wet with ether there 

 was a strong repulsive action; the powder was forcibly driven 

 aside, and the surface of the water was laid bare, evidently in a 

 state of agitation under the influence of the vapour of ether. I 

 tried many sorts of powders with a similar result, but none 

 answered better than lycopodium. 



My next proceeding was to try to represent the action of the 

 ether by means of films of oily compounds formed by the spread- 

 ing of an oily drop on the surface of water. A large soda-water 

 glass was first employed, but a common white dinner-plate showed 

 the effects best. Oil of turpentine, many of the turpentine var- 

 nishes, such as gold-size, black Japan, carriage, copal, &c, make 

 admirable films. Some of the fixed and essential oils also answer 

 very well. In experiments of this kind, a single drop of the oily 

 substance must be gently placed on, or rather delivered to the 

 water without any fall or disturbance ; otherwise the varnish, 

 &c. may sink below the surface in the form of a perfectly sphe- 

 rical bead, and so remain as a good example of cohesion. The 

 best method of obtaining a film is to dip a glass rod into one of 

 the oily liquids, and allow it to drain so that it may deliver only 

 a single drop to the surface of the water. The plate filled with 

 water should be placed before a good light, when a drop of the oily 

 substance, being gently placed on the centre, usually spreads 

 out with a beautiful exhibition of colour, or the film may be 

 quite colourless. Take the latter case. The finger, or, what is 

 better, a flat piece of sponge tied with thread over the rounded 

 end of a glass stirring-rod, wetted with ether and held over the 

 film, produces a cup-shaped cavity, within which a beautiful set of 

 Newton's rings may be seen so long as the sponge is wet with 

 ether. In this case the vapour of ether attenuates the film ; the 

 point immediately below the sponge is the point of greatest action, 

 and here the black of the centre of the first series of rings is seen : 

 the action diminishes from this depressed point, where the film is 

 thinnest, and it gradually increases in thickness until it unites 

 with the rest of the film, where colour ceases to be displayed. 

 The film is in fact under tension so long as the ether vapour is 

 acting upon it ; and the tension is greatest in the direction of a 

 vertical ray from the sponge to the water, and gradually dimi- 

 nishes as the rays increase in length from the sponge to the 



