388 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



the ends of which are made air-tight. by means of plates of rock salt which 

 do not intercept rays of heat. More than one-half of the heat from a 

 flame made by carbonic oxide is instantly cut off by the small quantitj' of 

 carbonic acid in the pxpired air. The amount of heat thus intercepted is 

 measured by a delicate thermo-multiplier. The air used in several experi- 

 ments was afterwards analyzed by Dr. Frankland, and found to agree very 

 nearly with the physical analysis, as wnll be seen by the following state 

 ment of the per cent of carbonic acid in the breath of a person under difler- 

 ent conditions. The first column is the result of the physical, and the 

 second of the chemical analysis : 



Breath before breakfast 4.00 4.31 



Breath after breakfast 4.66 4.66 



Breath after severe exercise i 5.33 5.22 



Hot Springs. 



The British Association for the Advancement of Science met at Bath on 

 September 14th. The President, Sir Charles Lyell, in his admirable inau* 

 gural address, referred to the thermal springs which, from the time of the 

 Eomans, have made Bath so celebrated, and stated that such springs usu- 

 ally occur where volcanic agency has caused a " fault ;" they are more 

 frequent where volcanoes are either active or have been so at a late geolo- 

 gical period. The quantity of solid matter in the hot springs alluded to, if 

 solidified, would form in one year a square column not less than nine feet 

 in diameter and 140 feet high. Although the waters of hot springs are, as 

 a rule, destitute of the common metals, such as iron, &c., there is strong 

 presumption that there exists some relationship between the action of ther- 

 mal waters and the filling of rents with metallic ores. The component 

 elements of metallic ores may, in the first instance, rise from great depths 

 in a state of sublimation, or of solution in intensely heated water, and may 

 then be precipitated in the water of a fissure as soon as the ascending 

 vapors or fluids begin to part with some of their heat. It is possible that 

 the metamorphism of sedimentary rocks may also be owing to the influence 

 of hot springs. The thermal waters of Plombieres in the Vosges were 

 conveyed by the Romans to baths through long aqueducts. In this case, 

 hot water, percolating through masonry, has given rise to various zeolites — 

 to calcareous spar, arragonite, fluor spar, and even opal. It is possible that 

 the consolidation of granite may have taken place at a less high tempera- 

 ture than was formerly supposed; and the manner in which volcanoes have 

 shifted their position throughout a vast series of geological epochs may, 

 perhaps, explain the increase of heat as., we descend to the interior of the 

 earth, without the necessity of our appealing to an original central heat, 

 or the igneous fluidity of the earth's nucleus. 



The Delta of the Amazon. 



This is the title of a paper read before the Geological Section of the 

 British Association, by Mr. Bates. He states that the delta is of a vastness 

 commensurate with the size of the river itself. It forms a triangle, each 

 side of which is about 180 miles, the mouth of the river being thus 180 

 miles in width. Within this gulf the island Marajo (as large as Sicily) 

 divides the river into two channels; the northern or Marie is 40 miles wide,. 



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