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THE POPULAR SCIENCE MONTHLY 



the entire sewage of Coventry in this way, 

 including rent of land and interest on capi- 

 tal, and without deducting receipts from the 

 sale of manure, is about Is. W. per head of 

 the population per year. But, taking into 

 account the chemical value of the manure, 

 the cost would be about twopence per 

 head. 



Construction of Water-Tanks. A water- 

 tank at the top of St. George's Hospital, in 

 London, recently burst, inundating the wards 

 and causing destruction of life and proper- 

 ty. This tank, which held about thirty-four 

 tons of water, was made of cast-iron plates 

 half an inch thick, bolted together in the 

 usual way ; in form it was a square of ten 

 feet on a side and the depth twelve feet. 

 The thickness of the iron plates was ade- 

 quate to resist the strain put upon them 

 only on the usual condition of the employ- 

 ment of tie-bars and nuts of the needed 

 strength. But, instead of adopting the 

 proper plan of bolting these tie-bars direct- 

 ly to the flanges by which the plates them- 

 selves were bolted together, thin plates of 

 wrought-iron, only one-quarter of an inch 

 thick, were bolted to these flanges, and the 

 tie-bars were attached to cross-pieces that 

 ran through holes in these plates. The 

 cross-pieces were so short that on the least 

 disturbance one end might slip out of its 

 place, leaving the entire stress on the other 

 end and on the thin plates in which it 

 rested. As was to be expected, the plates 

 gradually rusted, and, when the corrosion 

 had advanced so far as to allow the bolt to 

 be torn away by that strain on the sides of 

 the tank which the cross-bars were intended 

 to resist, the tank tore in two, and the water 

 made its escape. 



Movements of "fold Waves." Prof. 



Loomis, of Yale College, contributes to the 

 American Journal of Science and Arts, for 

 July, the fifth of his valuable series of papers 

 on " Meteorology." 



In a former paper he presented facts 

 showing the origin and probable cause of 

 extremely low temperatures. It was found 

 that they developed among the Rocky 

 Mountains, and moved thence, as " cold 

 waves," over the continent eastward. Since 

 the publication of that paper this phenome- 



non has become well understood, and is 

 now sustained by further proof. It appears 

 that low temperatures follow in the wake 

 of storms ; or, in other words, areas of high 

 barometer follow those of low barometer. 



By low temperature is understood a de- 

 gree of cold which is greatly below the 

 mean temperature of the place or area 

 where it prevails. Thus the cold wave of 

 December, 1872, started in Dakota on the 

 16th, and the temperature fell to 15, 25, 

 and finally 44, below the mean of the month. 

 At the same time the barometer rose to 

 30.64. 



The cold wave moved eastward and 

 southeastward, the barometer rising as the 

 cold came on. The cold was extreme from 

 the Rocky Mountains to Lake Michigan, 

 and from latitude 38 to the British posses- 

 sions. 



In New York, during the last six days 

 of the month, the depression of temperature 

 ranged from 18 to 24 below the mean of 

 the month. 



It is quite obvious, Prof. Loomis ob- 

 serves, that the cold experienced in Dakota 

 did not come from beyond the Rocky 

 Mountains, but on the easterly side, near 

 longitude 100. The greatest observed cold 

 in the instance referred to was not at the 

 most northern stations, which strengthens 

 the conclusion expressed in a former paper 

 that there is a source of cold independent 

 of the transfer of air from a higher to lower 

 latitudes. As the cold wave moves east- 

 ward, the intensity of the cold is found to 

 diminish. 



The professor calls attention to the very 

 interesting fact that, during the low temper- 

 ature of December, 1872, the stratum of 

 cold air was of no great thickness, probably 

 not more than 9,000 feet, as was shown at 

 Mount Washington. On the 26th of the 

 month, when the cold was at its maximum 

 over the region, it was found that the tem- 

 perature was higher by 20 Fahr. at the 

 summit of the mountain than at its base. 



Further facts are presented in this paper, 

 showing the general form of areas of low 

 barometer and of high barometer. It was 

 previously shown that a storm area is more 

 or less oblong, and not in any observed 

 case entirely circular. The same appears 

 to be true of the cold areas. 



