On Camphor Pulsations. 17 



ON CAMPHOR PULSATIONS. 



BY CHARLES TOHLLNTSON, 

 Lecturer on Physical Science, King's College School, London. 

 [We have much, pleasure in publishing the following interesting 

 letter from Mr. Tomlinson, who is quite right in stating that 

 the article in our May number to which he refers did not detail 

 all the precautions necessary for the successful performance of 

 the mora delicate experiments. Our object was rather to call 

 attention to his very good and accessible book than to supply 

 a substitute for it. We are glad to hear that the further inves- 

 tigation of the " Storm Glass " occupies his attention.] 



In the Intellectual Observer for May last you notice briefly 

 a few experiments from my small volume recently published, 

 entitled Experimental Essays; so briefly, indeed, that should 

 your readers endeavour to repeat them they may fail of success 

 through not taking all the precautions which I have detailed in 

 my book. For example, the experiment for exhibiting the 

 camphor currents is one that requires great care, and several 

 favourable conditions to make it succeed. In the first place, 

 the vessel must be quite clean; secondly, the water must be 

 quite clean, — it need not be distilled ; thirdly, the camphor must 

 be cut into the form of a stick, or a three or four-sided prism, 

 and be mounted in forceps, as shown in the engravings on page 

 38 of my book ; fourthly, the surface of the water must be very 

 faintly dusted with lycopodium powder, which is best done by 

 tying a small quantity of it up in a muslin bag, and gently 

 shaking it over the surface ; fifthly, the day must be fine and 

 dry. If all these conditions be observed the experiment will 

 succeed. As soon as the camphor is lowered into the water a 

 powerful repulsion of the lycopodium powder takes place, occa- 

 sioned by the formation of a camphor film, from which lines of 

 solution will stream out, and, being reflected symmetrically by 

 the side of the vessel, will throw the lycopodium powder into 

 pairs of revolving wheels, and the action will continue with 

 greater or less vigour so long as the camphor continues to be 

 immersed, provided the air be sufficiently dry to get rid of the 

 film by evaporation. In the course of some hours, depending 

 on the size of the camphor stick, the camphor will be cut across 

 at the surface of the water (as in Venturis experiment, de- 

 scribed in my first essay), and the lower portion thus becoming 

 detached will rotate about the surface of the water and destroy 

 the symmetry of the lycopodium wheels. On removing this 

 piece, and lowering the stick so as to dip just below the surface 

 of the water, the currents will set in afresh, and a new incision 

 be made in the camphor. In this way I have kept up these 

 currents for fifty or sixty hours. 



YOL. IV. — 2TO. I. C 



