412 Mr. C. Tomlinson on the Motions of Camphor 



13. In 1800 Carradori 14 approves of this explanation and 

 claims it as his own. The camphor owes its motion to the ex- 

 pansion of an oil drawn from it by the surface-attraction of the 

 water. He combat's Prevost' s theory (10), and denies that the 

 camphor on a bit of cork or other substance floating on water 

 has any motion. He insists on the energetic surface-attraction of 

 water. Oils, whether fixed or volatile, have a strong adhesion 

 or surface-attraction for water, but no cohesion or affinity of 

 aggregation for it. White wax and hard suet, which have no odour 

 and contain an od that is not volatile, rotate on water. Oils, 

 whether fixed or volatile, are more strongly attracted by the sur- 

 face of the water than camphor is, and hence they arrest its mo- 

 tion. And not only so, but starch and other vegetable products 

 and the juice of milky plants arrest the motions on account of 

 the strong surface-attraction. Many odorous bodies that do not 

 give out an oil to the surface of water have no motion. 



14. In ]801 Prevost 15 denies Carradori' s position (13), and 

 further supports his own case by stating that minute fragments 

 of camphor, benzoic acid, and dry musk rotate on clean dry mer- 

 cury, and indeed on any clean dry surface. He has seen under 

 the microscope minute fragments of camphor, too small for the 

 unassisted eye, rotate on various kinds of support. Camphor 

 will even rotate on small disks of mica placed on mercury. 



15. In 1801 Biot 16 confirms some of Prevost' s leading re- 

 sults, and gives the following experiment in support of his 

 theory : — If a very small pointed cone of camphor be presented 

 without contact to a thin film of water on a clean glass plate, it 

 will repel the water and leave a dry space round it. Hence he 

 concludes that camphor acts on water at a distance, and that its 

 movements on water are due to the mechanical reaction produced 

 on itself by the resistance which its vapour experiences in dart- 

 ing against the liquor which surrounds it, and that this emis- 

 sion of vapour is most abundant in the horizontal plane where 

 the air and the water meet. The camphor-cone will also repel 

 fragments of gold leaf floating in water without touching it or 

 them. 



16. In 1803 Carradori 17 replied to Prevost. It is curious to 

 note the common feature of this and other scientific controversies, 

 that one man cannot follow the reasoning or even repeat the ex- 

 periments of his antagonist, so difficult does observation become 

 when another man's results are looked at through the spectacles 

 of one's own theory. Thus Carradori denies that a capsule of 



14 Annates de Chimie, vol. xxxvii. p. 38. 15 Ibid. vol. xl. p. 3. 



16 Bulletin des Sciences par la Societe Philomatique, No. 54, p. 42. 

 Annates de Chimie, vol. xlviii. p. 197. 



