]S15.] Scientific Intelligence. 73 



contraction of a great artery, and its separation from tlie ligature 

 by the process of sloughing or ulceration. 



The details of this important case will no doubt be speedily 

 communicated to the profession, through some of the usual chan- 

 nels of scientific intelligence. 



III. Air Folcano. 



The Europeans who are not seasoned to the climate are accus- 

 tomed to leave Carthagena (in South America) during the heats of 

 summer, and to ^n-n'' that season at Turbaco, an Indian inland 

 village, delightfully situated on the top of a hill. Mr. de Hum- 

 boldt and his fellow traveller M. Bonpland, spent the month of 

 April, 1801. in this village. During their herbalizations, they 

 were informed by their Indian guides, that there existed a country 

 not far off, in the midst of a forest of palms, to which the name of 

 I'olcanitos {little volcanoes) was given ; that its surface had been 

 formerly covered with fire ; that a priest had extinguished the com- 

 bustion with holy water; and that now it ep>.itted nothing but 

 water. On going to the spot, our travellers found in the middle 

 of a vast plain, eighteen or twenty small cones, about 24 feet in 

 height. These cones are formed of a blackish grey clay, and have 

 an opening at their summits filled with water. On approaching 

 these small craters, a hollow but very disiii.ct sound is heard at 

 intervals, 15 or 18 seconds previous to the disengagement of a 

 great quantity of air. The force with which this air rises above the 

 surface of the water, may lead us to suppose that it undergoes a 

 great pressure in the bowels of the earth. Five explosions gene- 

 rally take place in two minutes, and this phenomenon is often 

 attended with a muddy ejection. According to the Indians, the 

 forms of the cones undergo no visible change in a great number of 

 years ; but the ascetiiJing force of the gas, and the frequency of 

 the explosions, appear to vary according to the seasons. Mr. de 

 Humboldt examined this gas, and found that it was azote mixed 

 with less than one thousandth of its bulk of oxygen gas. Here is 

 a phenomenon well worth the attention both of geologists and 

 chemists. Whence comes this azotic gas ? How is it produced ? 

 Does there exist in this place an immense magazine of ammonium, 

 whicii by means of water is converted into azote ? We are far in- 

 deed from being able to philosophize in the present state of our 

 knowledge, respecting the changes that take place under the sur- 

 face of the earth. 



IV. Mathematical Problem. 



(To Dr. Thomson.) 

 Sia, I'himout/i, Nov.2\, 1814. 



I beg, through tl"- medium of your Journal, to present to the 

 altcutiuii of the mathematical part of your readers, the following 

 1 



