1 92 Miscellanies. 



and once only in those by Irving, the mercury will rise in some pro- 

 portion to the depth to which the instrument is sunk. 



This I suppose to be true within certain limits only, for we are 

 justified in concluding from the experiments published, that at any 

 given time and place the temperature at one hundred fathoms' depth 

 does not differ materially from that of seven hundred fathoms, with 

 the exception, perhaps, of the equatorial and polar regions, where the 

 influence of a vertical sun or long continued cold may be felt at a 

 greater depth. 



At first view, the doctrine advanced in the article under notice, 

 may appear to be supported by the experiments given, for generally 

 the water was found colder at great depths than at the surface ; but 

 when it is remembered that the experiments were made during the 

 hot or temperate months of high southern as well as northern latitudes, 

 the cause of this general result will be obvious. 



General inferences from a few and (in this case from their na- 

 ture) imperfect experiments are always dangerous to the progress of 

 truth.* 



If the truth or fallacy of the theory of central heat be ever estab- 

 lished, it must be by experiments on a medium, less subject than the 

 ocean to variations of temperature, from the agency of tides, winds 

 and currents. 



II. By Dr. E. Emmons. 



Williams College, March 7th, 1830. 



It is familiarly known, that the upper surface of heating water is 

 hotter than the bottom, and that even ice may remain at-the bottom, 

 while the water near the surface would be quite uncomfortable to the 

 hand. Now the experiments of Peron prove the water of the ocean 

 to be in the same condition as water heating in a furnace, viz. with 

 the bottom the coldest and the upper surface the warmest, which cir- 

 cumstances are known to depend on the ascent of heated particles of 

 water to the surface, and the sinking of the colder to the bottom. 

 Now, until it is shown that a different effect would follow from heat- 

 ing the ocean at the bottom, from what takes place in our culinary 

 operations, I shall consider the experiments of Peron as misapplied 



* The caution suggested by Dr. Swift is equally applicable to both sides of this 

 question. It is certainly proper to observe and report all well ascertained facts on 

 the subject, although it may be long before any theory can be ftrmly established. — 

 Editor. 



