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THE POPULAR SCIENCE MONTHLY. 



as " gorgets " aad " banner-stones," were ap- 

 plied. By the aid of a committee of ladies 

 of Boston, the famous "Serpent Mound" in 

 Adams County, Ohio, has been bought, with 

 about sixty acres of land, put in order, in- 

 closed, and made the central object of an at- 

 tractive park. " The example," says Cura- 

 tor Putnam, in his report, " thus set for the 

 preservation of the ancient works of this 

 country, has already aroused others to ac- 

 tion, and many individuals and societies, par- 

 ticularly in Ohio, are now urging immediate 

 action to prevent the further destruction of 

 our archseologic monuments in the States." 



Origin of Lake Snperior Iron-Ore. — R. 



D. Irving, studying the ferruginous schists 

 and iron-ores of the Lake Superior region, 

 has found both of the theories that have 

 been put forward to account for them — that 

 of an eruptive, and that of a sedimentary 

 origin — inadequate. He proposes a new 

 theory, that the rocks have been derived 

 from original carbonates by a metastomic 

 process, or by replacement of the original 

 dolomitic or calcitic rock by siliceous and 

 ferruginous substances. The various steps 

 by which this process took place may have 

 been as follow : 1. The original form of the 

 beds was that of a series of thinly-bedded 

 carbonates, interstratified with carbonaceous 

 shaly layers, which were also often impreg- 

 nated by the same carbonate. This carbon- 

 ate was generally more or less highly ferrif- 

 erous, though probably there were interme- 

 diate forms between it and dolomite. 2. 

 By a process of silicification — which varied 

 in degree — ^these carbonate-bearing layers 

 were transferred into the various kinds of 

 ferruginous rocks now met with in the region. 

 3. The iron thus removed from the rock 

 at the time of silicification passed into solu- 

 tion in the percolating waters, to be rede- 

 posited in various places as it became fur- 

 ther oxidized, thus making ore bodies and 

 various impregnations. 4. In other places, 

 instead of leaching it out more or less com- 

 pletely, the silicifying waters seem to have 

 decomposed the iron carbonate in place, 

 producing a magnesia silicate, or a magnesia- 

 iron silicate, the excess of iron oxidizing im- 

 perfectly, and separating out as magnetite, 

 and the excess of silica crystallizing finally 

 as a minutely interlocked quartz ground 



mass. 5. The bodies of rich ore have prob- 

 ably had different origins in different cases. 

 6. Some of the silicifying process went on 

 before the folding of the formations ; but 

 some also afterward. It is not supposed 

 that this theory will not require modification 

 in the future, but it is the one to which the 

 author has been led, without being influ- 

 enced by any preconceived notions, very 

 gradually, during the growth of his expe- 

 rience with the minerals of the region. 



How long one can remain under Water. 



— The length of the time during which a 

 person can remain under water without chok- 

 ing — a subject on which exaggerated stories 

 have been told — ^has been studied by M. 

 Lacassagne. The author was favored with 

 an opportunity to examine Captain James, a 

 celebrated diver, whose exploits have ex- 

 celled those of all his rivals. He pretended 

 to be able to continue four minutes and four- 

 teen seconds under water. He contended 

 once in England for a prize which was of- 

 fered to any person who could endure five 

 minutes, but was compelled by a haemorrhage 

 of the nose and ears to rise at the end of 

 four minutes. He had also swum under 

 water during the same time a distance of 

 one hundred and fifty metres. He was ac- 

 customed before plunging to expel all the 

 air from his lungs and take a strong inspira- 

 tion. In the water he swallowed on the 

 average about a litre of the liquid. When 

 he came out of the water he snorted enor- 

 mously. In one of the experiments to which 

 M. Lacassagne subjected him, the move- 

 ments of the heart became slow, irregular, 

 and feeble at the end of two minutes ; and 

 on his coming out at the end of two minutes 

 and thirty-seven seconds, his face was con- 

 gested and his eyes flushed. Important facts 

 in the experiments were that in his full in- 

 spirations previous to plunging Mr. James 

 swallowed air, and while under the water a 

 considerable quantity of saliva ; and that his 

 respiratory movements did not cease during 

 immersion, but continued ample and regular 

 at the rate of twenty a minute, while the 

 thoraco - abdominal cavity diminished at a 

 gradual and regular rate. M. Lacassagne 

 explains these circumstances by supposing 

 that inspiration under water draws into the 

 lung the air contained in the pharynx, which 



