228 



of the summer sun, during the recess of the tide ; and Mr. Lyell 

 also obtained specimens, which were so satisfactory as to con- 

 vince English geologists that the fossil bird tracks were what they 

 had been considered to be by American geologists. 



Dr. C. T. Jackson said that he wished to correct the record 

 of November 1, 1848. The statement there attributed to 

 him as to the age of the Lake Superior Sandstone should be 

 accredited to his assistants, Messrs. Foster and Hill, as he 

 stated at the time. 



Prof. Wyman made some remarks on the probable cause 

 of the jet from the blow-holes of whales. 



During the past summer he had had an opportunity of observ- 

 ing this phenomenon while on a visit to Labrador. Three causes 

 for this jet had been assigned, namely, the water taken into the 

 mouth with the food of the animal, the water in the nasal cavi- 

 ties, and the secretions of the bronchial tubes. As it appears in 

 the form of a sudden discharge of vapor, he thought a fourth 

 explanation might be added, the sudden rarefaction of the air 

 when inhaled, followed by its sudden condensation when emitted. 

 He thought it was partly due also to the small quantity of water 

 which entered the outer extremity of the nasal passages. He had 

 succeeded in imitating the appearance in question, by introducing 

 a small quantity of water into the end of a syringe and suddenly 

 expelling it with the body of air behind it, with considerable 

 force. 



Dr. Pickering said that he could not think the condensation of 

 the air when expelled from the lungs of the whale was a circum- 

 stance of much importance in forming the jet, as in tropical 

 climates, where this could hardly occur, the jet was as complete 

 as in colder latitudes. 



Prof. Wyman said, that at Bras d'Or he had heard the inspira- 

 tion as well as the expiration of Cetaceans. It follows the expi- 

 ration instantaneously but is much shorter and less audible. 



Mr. Ayres, from his own observations, confirmed Prof. 

 Wyman's views. He said he had noticed in a young porpoise 

 that the act of breathing is much more slowly performed than in 

 the adult. 



