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THE POPULAR SCIENCE MONTHLY. 



power of the north wind ; and the same 

 cause checks the growth of fungi. The 

 economical value of the north wind is dis- 

 cernible in its power to preserve from rapid 

 decay houses, barns, fences, etc., and the 

 same influence must protect iron from de- 

 structive rusts. 



Effects of Lightning on Different Species 

 of Trees. The effects of lis>htning on vari- 

 ous species of trees have been made a sub- 

 ject of investigation by Daniel Colladon, 

 who communicates to the Geneva Society 

 of Natural History the results of his ob- 

 servations. He states that, when a poplar 

 is struck, all the upper part of the tree re- 

 mains perfectly sound and green. The 

 height above the ground at which the in- 

 juries appear does not, in large poplars, ex- 

 ceed the third of the tree's height. These 

 injuries commence immediately below the 

 junction of the strong branches with the 

 trunk. In general they do not reach quite 

 to the ground. It is always the tallest pop- 

 lar that is struck. In some cases the storm 

 will pass over trees of other species, and 

 will explode on poplars, though they be of 

 less height. M. Colladon has never met 

 with any traces of carbonization. The 

 cases in which several poplars have been 

 injured by a single discharge of lightning 

 are rare. One such case is recorded by the 

 author where three poplars were damaged 

 by the same stroke. These trees stood in 

 a straight line, and about twelve feet dis- 

 tant from each other. 



How they teach Geology in Rome. The 



eminent archaeologist, G. Mortillet, gives 

 an amusing account of a class-lecture on 

 geology which he once attended in the Ro- 

 man University of the Sapienza. " I suc- 

 ceeded," he writes, "not without difficulty, 

 in getting leave to be present at a lecture 

 on geology. I was introduced into a large 

 hall ; in the middle stood a small table, at 

 which four persons were seated. On the 

 one side sat the professor in an arm-chair, 

 and on the other three students in common 

 chairs. Near the professor's seat was a 

 more comfortable arm-chair for the inspect- 

 ing prelate, who from time to time came to 

 see that the teaching went on aright. As a 

 stranger supposed to be well-disposed, I 



was honored with a seat in the grand arm- 

 chair, I expected to listen to an interesting 

 lecture in good Italian ; the more, inasmuch 

 as the professor, Ponzi, now a Senator of 

 Italy, is a distinguished man, and a savant 

 of repute. But I was disappointed. The 

 professor, for upward of half the time of the 

 lesson, was obliged to dictate for such was 

 the rule his lecture, which had been writ- 

 ten in advance in Latin, and revised and 

 corrected by the censor. During the latter 

 half he was permitted to give in Italian ex- 

 planations of the dictated paragraphs; but 

 he was not at liberty to diverge from his 

 text, nor could the students take notes. 

 These things I have seen with my own eyes 

 at Rome under the reign of Pius IX., author 

 of the ' Syllabus.' " 



Effects of Compressed Air on Animals. 



The mechanical effects of compressed air 

 upon the animal economy, as ascertained 

 by Bert, are to cause a lowering of the dia- 

 phragm and liver, and a consequent in- 

 creased pulmonary vital capacity ; this ef- 

 fect, while gradual in its production, lasts 

 long after the subject is withdrawn from 

 the compressed-air bath. Pravaz finds that 

 the heart's action is at first increased, and 

 then lessened, the pulse first becoming more 

 rapid, and then slower, but never falling be- 

 low the rate at normal pressure. The res- 

 pirations are diminished during immersion, 

 but on removal of the increased pressure 

 they rise in frequency and in direct propor- 

 tion to the degree of compression. There is 

 an increase in the amount of urea excreted, 

 but this increase diminishes the longer the 

 sojourn in the compressed air. There is at 

 the same time an increase in the amount of 

 carbonic acid expired. The temperature 

 of the body rises above the normal at first, 

 and then falls as the immersion is prolonged. 

 These varying effects are due, Pravaz thinks, 

 to the two influences of inward atmospheric 

 pressure and hyper-oxygenation, the former 

 tending to diminish the circulation and the 

 organic changes, and the other to increase 

 them. 



Occurrence of Nickel- Ores. Nickel-ores 

 occur in great abundance in New Caledonia, 

 and are being actively worked. These ores 

 in no way resemble those from which nickel 



