11 
a welcome addition to our petrological collections* The Museum mineralogist. 
Dr* W. F* Foshag, tells me that the rock is a trachyte, an igneous rock that 
has become more or less phosphatized as the result of being acted upon by 
solutions of alkaline phosphates such as ammonium phosphate and other com- 
pounds derived from the droppings of the sea birds so plentiful on Clipperton* 
Several of the booby birds 1 crude nests were brought back for exam- 
ination of their insect inhabitants. Already, a tiny mo Husk, several insects 
earthworms, and even amphipods were sorted from this debris* Dry grass, 
odds and ends of plants and plant stalks, a few feathers, and even bits of 
driftwood, such as a bit of shingle in one case, go into the bedding of a 
booby nest. 
About the time we prepared to leave the island, conditions were 
such that we could almost walk out to the launch anchored outside the breakers 
but the bottom was treacherous and full of deep holes into which one stepped 
without warning to go in over has head. All hands had a grand time; the 
excitement of getting ashore and off again just added to the fun. 
A.s far as fishing was concerned at Clipperton, a shark convention 
holding forth at the time of our visit about ruined the sport* As soon as 
a fish was hooked, some shark would either H chop* } it to pieces or cut the 
line* Indeed, the first fish of the day was a 60~lb* shark hooked by the 
G'r Secret a ry 
President as his boat shoved off from the ship* Later, Mr. Early landed a 
175~pounder after a well nigh exhausting session* Both proved to be tiger 
sharks. Gale peer do arct icus * The smaller specimen was still young enough to 
be in the spotted and black-barred phase which gives the species its charac- 
teristic name. These rather striking markings are lost as the ground color 
of the adults darkens with age to become nearly a uniform grayish brown! He 
under parts are a grayish white to white. 
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