May 31, 1900J 



NATURE 



115 



they occupy but a very small fraction of the contents of the 

 cubic centimetre, but yet their number is so great that they 

 would, if placed in line touching one another, go round many 

 times the circumference of the earth, a pretty fair illustration of 

 Euclid's definition of a line. 



These molecules, however, are not at rest, but are moving, 

 even at the low temperature I have named, with great 

 velocity, the molecules of the different gases moving with 

 different velocities dependent upon their molecular weight. 

 Thus, the hydrogen molecules which have the highest velo- 

 city move with about 5500 feet-seconds mean velocity, while 

 the slowest, the carbonic anhydride molecules, have only 

 1 1 50 feet-seconds mean velocity, or about the speed of 

 sound. 



But in the particular gun under discussion, when the charge 

 was exploded there were no less than 20,500 cubic centimetres 

 of gas, and each centimetre at the density of explosion contained 

 580 times the quantity of gas— that is, 580 times the number of 

 molecules that I mentioned. Hence the total number of mole- 

 cules in the exploded charge is 8^ quadrillions, or let us say 

 approximately for the total number eight followed by twenty- 

 four cyphers. 



It is difficult for the mind to appreciate what this immense 

 number means, but it may convey a good idea if I tell you that 

 if a man were to count continuously at the rate of three a 

 second, it would take him 265 billions 

 of years to perform the taslc of counting 

 them. 



So much for the numbers ; now let 

 me tell you of the velocities with which, 

 at the moment of explosion, the mole- 

 cules were moving. Taking first the 

 high- velocity gas, the hydrogen, the 

 molecules of the gas would strike the 

 projectile with a mean velocity of about 

 12,500 feet-seconds. Vou will observe 

 I say mean velocity, and you must note 

 that the molecules move with very vari- 

 able velocities. Clerk Maxwell was the 

 first to calculate the probable distribu- 

 tion of the velocities. A little more 

 than one-half will have the mean velocity 

 or less, and about 98 per cent, will have 

 25,000 feet -seconds or less. A very few, 

 about one in 100 millions, might reach 

 the velocity of 50,000 feet-seconds. 



The mean energy of the molecules of 

 different gases at the same temperature 

 being equal, it is easy from the data I 

 have given to calculate the mean velo- 

 city of the molecules of the slowest 

 moving gas, carbonic anhydride, which 

 would be about 2600 foot-seconds. 



I have detained you, I fear, rather 

 long over these figures, but I have 

 done so because I think they throw 



some light upon the extraordinary violence that some explo- 

 sives exhibit when detonated. Take, for instance, the lyddite 

 -hell exploded by detonation I showed you earlier in the 

 evening. I calculate that that charge was converted into gas 

 in less than the 1/60, 000th part of a second, and it is 

 not difficult to conceive the effect that these gases of very 

 high density suddenly generated, the molecules of which are 

 moving with the velocities I have indicated, would have upon 

 the shell. 



The difference between the explosion of gunpowder fired in a 



close vessel, and that of gun-cotton or lyddite when detonated, 



is very striking. The former explosion is noiseless, or nearly 



The latter, even when placed in a bag, gives rise to an 



sceedingly sharp metallic ring, as if the vessel were struck a 



irp blow with a steel hammer. 



But I must conclude. I began my lecture by recall- 

 some of the investigations I described in this place 



great many years ago. I fear I must conclude in much 

 same way as I then did, by thanking you for the 

 Itention with which you have listened to a somewhat dry 

 ilbject, and by regrettioo; that the heavy calls made on 

 time during the last few months have prevented my 



iking the lecture more worthy of my subject and of my 



lience. 



EXTENSIONS OF THE DYEING DEPART- 

 MENT OF YORKSHIRE COLLEGE, 



'T'HE opening of the extensions in the Clothworkers' Depart- 

 ^ ments of Yorkshire College, Leeds, has already been re- 

 ferred to fp. 69). The new buildings, which are shown in the 

 accompanying illustration, comprise practical and pattern dye- 

 houses and a research laboratory ; and, as with several other 

 parts of Yorkshire College, they owe their erection to the 

 generous interest taken in technical education by the Cloth- 

 workers' Company of London. 



The Clothworkers' Departments of the Yorkshire College 

 consist of textile industries, dyeing and art. The buildings 

 occupied by these departments have been erected by the Cloth- 

 workers' Company at a cost of about 60,000/. ; they are spread 

 over an area of about one-and-a-half acres, and have been 

 specially arranged and equipped for the teaching of all the 

 subjects connected with the designing and manufacturing of 

 woven fabrics. 



The Dyeing Department of the Yorkshire College was estab- 

 lished in 1880, and the head of the department is Prof. J. J. 

 Hummel. Although the accommodation at first providied was 

 extremely limited, it nevertheless sufficed to show that a demand 

 for instruction in dyeing really existed, and that a continuous 

 supply of students for this subject was available. In due time 



Buildings of the Dyeing Department of Yorkshire College. 



it was found desirable to increase the facilities for experimental 

 work, and in 1885 the Clothworkers' Company of London 

 erected and equipped, at an expense of about 12,000/., the front 

 portion of the handsome and commodious building at present 

 occupied. 



It was felt some years ago that the work of the different 

 departments might be connected. It was considered desirable, 

 for example, that the coloured yarns employed in the weaving 

 department should be dyed by the students in the dyeing 

 department, so that, if at the same time these yarns could also 

 be manufactured on the premises by the establishment of a 

 spinning department, it would become possible to teach the 

 whole routine of clothworking, from the wool in the raw state 

 to the finished cloth. Acting upon this idea, the Clothworkers' 

 Company decided to make the necessary provision for carrying out 

 the scheme suggested, and to extend both the weaving and dyeing 

 departments, at a cost of about 25,000/. In connection with 

 the dyeing department, it was arranged to build a three-storied 

 building, to provide two additional dyehouses in which practical 

 dyeing could be carried on, and also a research laboratory for the 

 prosecution of scientific investigations connected with dyestuffs 

 and dyeing. 



In July 1S96. the foundation stone of the new Clothworkers' 

 Research Laboratory and the other extensions was laid by the 



NO. 



1596. VOL. 62] 



