72 



KNOWLEDGE. 



[Apkil 1, 1892. 



1 28 cubic iuclies of gas. ' We find,' says the article, ' Gunpowder,' 

 in the ' Edinbiirgh Encjclopfedia,' ' that 1267 of gunjjowder 

 generates 109'6 cubic inches of gas. from which one grain of gun- 

 powder woukl jield 1'25 cubic inches of gas. This, he shouUl assume, 

 was correct. Then 253 grains of gunpowder (the weiglit of a cubic 

 inch of water) wouhl produce 316'25 cubic inches of permanent gas. 

 But one cubic inch of water, expanded into steam, occupied the space 

 of 1728 cubic inclios ; hence the elastic force of water was to that of 

 gunpowder as 1728 to 316'25 or 5^ to one nearly. It would, therefore, 

 lequire only 366 cwt. of water to do the work of one ton of 

 gunpowder. To do the work of eight tons of gunpowder would be 

 required 2988 <'wts. of water, or 328 gallons, or about six hhds. of 54 

 gallons each, or 52^ cubic feet of water. ^N'ow, there could be no 

 difficidty in imagining that this quantity of water would get into the 

 Taidt, and cause the explosion." 



EXPERTMEXT,S AT THE FeLLING ChEMICAL WOEKS. 



■' On arriving at the extensive chemical works of Mr. Pattinson at 

 the Felling, that gentleman at once proceeded to make experiments, 

 in presence of the coroner, the jury and Captain Du Cane, in support 

 •of the evidence he had given on the preceding day. He first 

 •caused a metal pot to be inserted in the ground until its top was 

 level with the surface, and having put into it 9 lbs. of nitrate of soda 

 and () lbs. of suljjhur, he ignited the mass ; and then heating it to the 

 highest possible degree of which it was .susceptible, he poured into it 

 about a quart of water. The effect was immediate explosion, accom- 

 -panied by a loud clap, whicli would have been exceedingly perilous 

 to any jjerson in its inunediate vicinity. The experiment was repeated 

 under precisely simUar conditions, and attended with a precisely 

 similar result. A trial of the same kind, which had been made 

 before the arrival of tlie coroner and jury, had been accompanied 

 -with the additional effect that the metal vessel, wliich was the subject 

 •of it, had a hole blown through it in two or three different jilaces. 

 A series of experiments was then made under slightly different 

 conditions. The pot, into wliich the sulphur and nitrate of soda were 

 put, was covered over the top with a large piece of thick metal of 

 considerable weight, and above that again were placed several large 

 pieces of clay and earth. It was deemed necessary to try this 

 experiment in an open field, away from any dwelling-house, and 

 which admitted of the spectators placing themselves at a safe 

 distance from the spot. The materials were then ignited as before, 

 and when in the incandescent state water was potired \ipon the 

 mass down a spout ; but the i-esult was only a comparatively 

 slight explosion, and which scarcely disturbed t'lie iron and clod's 

 placed over the mouth of the vessel. Another experiment of the 

 kind was made with the same result. At length, a trial having been ! 

 -made for a third tinu\ but with this difference, that the vessel was i 

 covered over tlie top « ith another similar vessel, and tluit the water 

 was poured upon the sulphur and nitrate of soda with greater rapidity 

 •than before, by slightly elevating the spout, the effect was to blow up 

 •the pot on the top into the air to a height of ujiwards of 70 feet, 

 Accompanied by a loud detonation. ■\\'ith this the coroner and jury 

 •seemed convinced that whether or not the premises in Hillgate 

 •contained gunpowder, they contained, at all events, elements as 

 •certainly explosive, and, perhaps, far more destructive." 



N.B. — A large water-pipe inside the building appears to have 

 •burst ; thus adding to the water from the fire engines. 



[There is some difficulty in understanding how without ! 

 ■a prior shock, or dislocation, water could in any quantities ' 

 enter heated cavities in the earth. A little -^-ater percolating 

 in would, if converted into steam, tend to drive back and 

 ■check the entrance of more -water from above ; and to 

 produce a great explosion a considerable mass of water 

 •would need to be admitted rather sitddenly to a hotter 

 region. The slipping of strata, or any sudden change 

 along a line of fault might, no doubt, afford a way 

 for such a down rush, but one has to account for 

 the initial movement. If, as is so often assumed, 

 there is an average rise of temperature as we descend 

 within the earth, amounting to 1° Fahrenheit for every 

 50 to (JO feet, water would be raised to 212° Fahrenheit ', 

 at a depth of much less than two miles (i.e., some- 

 where between 7500 and 9500 feet). Water under pressure 

 would glow with a red heat at a depth of ten miles, and cast 

 iron would glow white, and be raised to a temperature which 

 would melt it at the earth's surface, at a depth of 30 miles. 

 But the ordinary assumption with regard to a rapid in- 

 crease of temperature is founded upon observations made 

 within such mere scratches in the earth's crust, that we ! 



cannot safely assume that the temperature will increase 

 uniformly as we proceed to greater depths. Our deepest 

 mines only extend to a depth of a little more than half a 

 mi!e from the surface, while our deepest borings do not 

 extend to four-fifths of a mile in depth. In entering this 

 mere outer skin of the earth it is found that there are 

 great inequalities in the observed rise of temperature in 

 different regions of the globe, such as certainly would not 

 exist if the increasing temperature were only due to the 

 secular cooling of the interior of the earth from an 

 originally-heated mass. Thus, according to Prof. Judd, 

 at the great boring of Grenelle at Paris, the increase of 

 temperature down to the depth of 740 feet amounted to 

 1° Fahrenheit for every 50 feet of descent, but from 

 740 feet down to 1600 feet the rate of increase diminished 

 to 1° for 75 feet of descent. In the deep boring of Speren- 

 berg, near Berlin, whicli attained the great depth of 

 4052 feet, the increase of temperature for the first 

 1900 feet was 1° Fahrenheit for every 55 feet, and 

 for the next 2000 feet it diminished to 1° Fahren- 

 heit for every 62 feet of descent ; w'hile in the deep 

 well of Buda - Pesth a decline in temperature was 

 actually found below the depth of 3000 feet. On the 

 other hand, at Monte Wassi, in Tuscany, the temperature 

 was found to increase at the rate of 1° Fahrenheit for 

 every 24 feet of descent, while in the Comstock Mine there 

 is a rise of temperature of 1^ Fahrenheit for every 45 feet 

 of descent between 1000 and 2000 feet from the surface, 

 and a similar rise for every 25 feet at depths below 2000. 

 Such irregular increases of temperature seem to show 

 that there are great local sources of heat, due possibly to 

 chemical changes going on, or more probably to the great 

 crushing and crumpling of strata along lines of weakness, 

 which are always taking place ; raising mountain ridges 

 and depressing other regions as the external shell of the 

 earth contracts by secular cooling upon the central mass. 

 It is a fact well know-n to geologists, that rocks which 

 appear to have been subjecteil to great movement and 

 contortion also appear to have undergone great chemical 

 change, such as would follow from their being subjected to 

 a high temperature in the piresence of water. With such 

 evidence of stress and change going on within the body of 

 the earth, we need not necessarily look to explosions as 

 the cause of the tremors which occasionally agitate the 

 earth's surface. — A. C. Eanyakd.1 



OUR NEiHEST NEIGHBOURS AMONG THE STARS. 



To the Editor of Knowledge. 



Dear Sir, — The late Mr. Proctor pointed out long 

 ago that the best test of the relative distances of the 

 stars which we possess is their relative proper motions. 

 Not of course that there may not be near stars, whose 

 proper motions are small, because they are moving 

 almost directly towards us or away from us, but that 

 every star, with large proper motion, must be comparatively 

 near, unless we ascribe to it an enormous velocity. 

 This is true, even if the apparent proper motions of these 

 stars are largely due to the sun's motion in space, for it 

 is only on near stars that the effects of this motion will 

 be easily perceptible. When travelling by train, the trees 

 at the end of the next field appear to be moving rapidly, 

 while the distant range of mountains hardly changes its 

 apparent place. In like manner an extremely distant 

 star will appear to be unaffected by the sun's motion, 

 while a near one will be considerably displaced. This con- 

 clusion, moreover, is borne out by the results of spectro- 

 scopic research. The spectroscope reveals no extraordinary 



