A PROBLEM IN PUMICE 175 



coloured species such as O, macrocera. But among 

 those descendants of the original stock that happened 

 to be brightly coloured, some individuals would certainly 

 — since inequality of powers and performance is one of 

 the facts of nature — have scratched deeper holes than 

 others ; and as those which did not scratch deep would 

 be the most likely to be seen and destroyed, we should 

 in the course of long generations have only the very good 

 diggers left to form an active, deep-burrowing species. 



One of the most singular observations made on 

 Cardamum Island was due to Lieuts. Smith and Sinclair, 

 who discovered, a little inland of the northern end of the 

 island, a bed of pumice-stone. Lieut. Sinclair was par- 

 ticularly and very literally impressed by it, because, 

 going ashore to take stars " one evening, he had to 

 sit upon it, nor was he able either to dig down to softer 

 ground beneath, or to find a convenient spot that was 

 free from it. Both officers were quite sure that it w^as 

 pumice, and even the lascars, who are constantly using 

 the article, took notice of it. Unfortunately when I 

 heard about it next morning, Cardamum Island was 

 far astern of us. How did the pumice-stone get there, 

 above the ordinary high-water mark on an almost un- 

 inhabited island? This, like Sir John Falstaff, I must 

 leave — a question to be asked ; for I unhesitatingly 

 dismiss the explanation which has since been made, 

 that two intelligent and experienced naval officers do 

 not know what pumice is. 



