1846.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



Ill 



which any diminished temperature of that planet would have occasioned. 

 Mr. Taylor quoted also records which proved that the climate of Tuscany 

 has undergone no change during the last 200 years. With respect to the 

 temperature of the sea, many difficulties are offered to accurate observation. 

 The uncertainty as to the depth to which thermometers can be sunk, the 

 influence of cold and warm currents, the laws regarding the circulation of 

 heat in liquid.i, and the effects of heat on the density of water, present 

 serious obstacles to accurate results. The most careful observations and 

 calculations give an oceanic temperature of from 34 deg. to 44 deg. It is 

 probable that the submarine strata are sufficiently thick to prevent the free 

 conduction of central heat, while the effects of heat on the density of water, 

 together with its rapid diffusion throughout the mass of the ocean, would 

 render a high temperature imperceptible at any one point. On the other 

 hand, the abundance of insular volcanoes sufficiently testifies the existence 

 of igneous matter beneath. 



From these considerations, Mr. Taylor concluded — 



1. That, at a certain de|/th below the surface of the earth, there is a 

 source of heat which increases as we descend. 



2. That this heat cannot be derived either from the sun or from chemical 

 changes. 



S. That this heat neither perceptibly affects climates or seasons, nor in- 

 fluences the lemperature of the surface of the earth, nor of the depths of the 

 ocean, nor of the atmosphere. 



4. That the vicissitudes of climates and seasons are entirely referrible to 

 solar influence. 



5. That this influence, even at its maximum, does not penetrate below 

 l-400,000th of the earth's diameter. 



fl. That, although we have positive evidence that subterranean heat ex- 

 ists, we can neither measure its intensity, nor determine the exact ratio of 

 its increase towards the centre of the earth. 



7. That there is no evidence to show that the earth is gradually cooling 

 from a high temperature. 



EXPLOSION IN A SEWER AT IXELLES. 



A report has recently been published in a Brussels Journal on the 

 causes of an explosion which occurred on the 2nd of January last, at 

 Ixelles. The following account is taken from this report, which however 

 we have not translated very faithfully, as in several places we have made 

 omissions for the sake of brevity. The report is signed by M.M. Nollet, 

 Dieudonn^ and Spaak : their principal object seems to be to remove all ap- 

 prehension as to the possibility of explosive gases being generated in 

 sewers. 



It is stated that the street gas pipe under the Etterbeek road was broken, 

 aud that in consequence there was an abundant escape of gas wliich pene- 

 trated the sewer in which the explosion took place. Another main gas 

 pipe under the Ixelles road was also broken; but this second accident 

 might have resulted from the explosion, which caused a great deal of 

 damdge in the neighbourhood. The sewer in which the explosion took 

 place had been in use only twelve days. The commissioners on entering 

 the sewer in which there was rooji to stand upright, found in it water 

 slightly blackened ; but the flame of a candle burned in it as brightly as in 

 the external air, respiration was not impeded, and there was but very little 

 odour. 



The water from the Ixelles road after passing through trapped gratings 

 falls into a brick cistern, from which the overflow, after leaving the heavier 

 deposits in the cistern, passes into a conduit from which the liquid de- 

 prived of the insoluble matter* passes into the sewer. 



Much rain had previously fallen. The water was consequently con- 

 stantly renewed ; the temperature of it was also below zero (centigrade), 

 and there was little vegetable matter present. 



Two questions presented themselves. Was it possible, as had been 



*-0n ttle other baQd it is stated in a memoir, by IJupuytrea, on the mephitic air of 

 cesspools (Journal de Medecine, Vol. XI.) that on analysing the air iu one of tliese [Jaces 

 tilere were— 



Aeote . , . . 94 



Oxygen . . . . . , 2 



Carbonate of ammoata . . . . 4 



Id znother case there were — 

 Azote 

 Oiygen 

 Carbonic acid gas 



100 



IDO 



suggested, that carbonated hydrogen could have been generated in the 

 sewer itself, and there formed an explosive mixture? Again, in what 

 manner could this mixture have been produced .' 



The reply to the first question is, that carbonated hydrogen could not 

 have been formed either in the sewer or the branch pipes ; that neither the 

 nature of the substances, nor their stagnation, nor the degree of tempera- 

 ture, nor the length of time, four conditions requisite for the supposed de- 

 composition, permitted this hypothesis. 



If it be true that in the Pontine Marshes and other marshy places where 

 there is a large quantity of mud, composed principally of the detritus of 

 vegetable matter, and constantly covered by water heated by the sun, 

 bubbles of carbonated hydrogen escape, especially when the mud is stirred, 

 it is when the four conditions determined above concur to produce the 

 phenomenon. 



But it may be said that sewers contain faeces and other animal sub- 

 stances. The examination of the nature of the gas emanating from these 

 substances has been undertaken by a commission appointed in Paris to 

 superintend the purifying of ancient sewers. The average of 21 experi- 

 ments gives the following result -.^ 



Oxygen .. .. .. 18-10 



Azote .. .. .. 7870 



Carbonic acid gas .. .* 2*30 



Sulphuretted bydrogea .. . . -yO 



100-00 



In no instance was the gas inflamed during the visits: on the contrary 

 it was remarked that the flame of a candle burned feebly and sometime* 

 was extinguished. This was a necessary consequence of the compositioa 

 of a gaseous mixture in the sewer of Kue du Chemin Vert at Paris, of 

 which the following is the analysis. 



Oxygen .. .. .. 13-79 



Aiote .. .. .. 81-21 



Carbonic acid gas . . . . 2-01 



Sulphuretted hydrogen .. .. 2-99 



This gas was asphyxiant ; it instantly extinguished the flame of a taper. 



In one instance only M Serpette, Inspector-General ofSewers, at Paris, 

 found a gas which inflamed on the introduction of a lamp ; the flame of the 

 gas went out and again caught fire, but this phenomenon which never oc- 

 curred, but iu this one instance, took place in a sewer of the Rue du Pon- 

 ceau, where the mud was very deep aud had long been undisturbed, and 

 the gas burned without explosion. All the facts are detailed in the work 

 published by Parent du Chalelet on the sewers of Paris, and in his treatise 

 on public health published iu 1836. 



One more instance is known of fire occurring in a sewer at the approach 

 of a flame, but this occurred from the passage into this sewer of a liquid 

 refuse containing a large quantity of tar produced at some neighbourii>g 

 gas works. 



With respect to the explosion in the main sewer at Ixelles, it is ascer- 

 tained that the main gas pipe was broken before the explosion near the 

 drain of the Etterbeek road took place. Several days before the accident 

 occurred a stiong odour of street gas was perceived in the neighbourhood. 

 This odour is easily distinguished from that of drains, and it was so stroog 

 that notice of the escape of gas had been given at the gas works. It is to 

 the mixture of this gas with the air of the drain that the explosion must be 

 attributed. 



To prevent the recurrence of so serious an accident, it ii proposed to 

 make the gas tubes of increased thickness where they traverse cross streets, 

 and to imbed them in brickwork. It is also proposed to replace the exist- 

 ing close covers of the drains by openings which will facilitate the renewal 

 of the air. The inside of the drains also has been carefully coated with 

 plaster, so that there is no cause to apprehend that a detonating mixture 

 can be again formed under circumstances resembling those which led to 

 this disastrous explosion. 



Height of Vesdvids. — According to the latest observations of the 

 scientific men charged with the geodelical works of the kingdom of Na- 

 ples, the height of Vesuvius, at its most elevated point — a point which has 

 undergone no change for many years — the punta del Palo, is 1203;^ metres 

 (3948 feet) above the mean level of the sea. 



