216 Wm. A. Norton on the Variations 



Vol. III. — Descriptions of several new species of Ascidia. 

 Description of a new species of Cephalopod of the genus Loligo. 

 On three new species of parasitic Vermes, belonging to the Linnean germs Lernsea. 

 Descriptions of two new species of the genus Batrachoid of Lacepede. 

 Vol. IV. — Description of several species of the Linnean genus Kaia, of North 

 America. 



Description of several new species of Holuthuria. 

 Description of two new species of the Linnrean genus Blennius, 

 Vol. V. — Description of a new fish of the genus Salmo. 

 Description of four new species of Mursenophis. 

 Description of a new species of the genus Saurus. 



Transactions of the American Philosophical Society, new series. 



Vol. I, (1818.) — Description of several species of Chondropterygious Fishes of 

 North America, with their varieties. 



A celebrated naturalist having expressed an opinion that the cliffs 

 of Normandy were uninteresting, on the score of organic remains ; Mr. 

 Lesueur, who was of a different sentiment, undertook an investigation 



of the stratification of the bluff forming Cope la Heve ; and his dis- 

 coveries were of a nature to call the attention of geologists to a local- 

 ity which had been neglected and decried. In the latter part of the 

 year 1843, he published a sheet, entitled, " Vues et Coupes du Cap de 

 la Heve." This lithographic drawing presents numerous details of 

 uncommon interest ; and is a pleasing evidence of the versatility of the 

 talents of the author. 



Art. XVI. 



Declination of 



Magnetic Needle, and in the Intensities of the Horizontal 

 Vertical Magnetic Forces ; by William A. Norton, Pro- 

 fessor of Mathematics and Natural Philosophy in Delaware 



College. 



[Continued from p. 55.] 



Besides the phenomena which have now been considered, 

 there are two others, to which the laws of the nocturnal loss of 

 temperature may be conjecturally attributed, viz. 1. The varying 

 humidity of the soil at the earth's surface, attended with a change 

 in its specific heat, and — 2. An unequal exchange of heat be- 

 tween the atmosphere and the earth, by contact. That the first 

 of these is to be rejected from the list of possible causes, will be 

 seen at once upon considering that there is no evidence that the 



depe 



temperature 



There is no sufficiently general increase of humidity, except from 

 dew, and the film of dew is too slight (as we shall see, not more 

 than in 0l, on the average, in July) to produce any material 

 change in the specific heat of an inch, or half an inch, of thick- 

 ness of the soil. Besides whatever influence may arise from this 

 cause may be set down as an effect of dew. 



As for the second of the above mentioned conjectures, the fol- 

 lowing objections lie against it. In the first place the quantity of 

 heat received from the air by simple contact, when the air is per- 

 fectly tranquil, is very small, by reason of its low conducting 



