320 



NA TURE 



[August 4, 



very large industry. It is not proposed to discuss the two sides 

 of the question — the maintenance of the industry or the pre- 

 servation of the purity of such a fine river as the Spey, or other 

 rivers similarly situated — but rather to consider what can be 

 done to meet both sides. Now it may be held as true that there 

 is no operation to which the burnt ale or spent lees of a distillery 

 can practically be subjected to, that will render the effluent 

 innocuous. The effluent may be evaporated or spread over 

 irrigation fields, or treated with chemicals or charcoal, and yet 

 the processes are in one way or another defective ; and there 

 appears but one solution, not to pass the effluent into the rivers, 

 but take it away in pipes or barges to the sea. In many cases 

 this is quite impracticable, even by the joint action of a number 

 of distilleries ; but in some cases the effluent has successfully 

 been taken miles in pipes and discharged into the sea. As is 

 known from large experience in outfall pipes for sewage and 

 paper works effluents, it requires a carefully designed arrange- 

 ment, the cost of which can only be determined after a minute 

 survey ; and usually the cost turns out to be too great, and then 

 there appears to be one solution by passing the effluent out in 

 the forni of a fine spray from the top of a high chimney or iron 

 lattice tower. The natural question at once asked is : But you 

 pollute the air instead of the water, and what the better are you 

 for doing so ? In the first place, what is discharged is not a gas 

 which, if of a noxious quality, might hurt by being inhaled. 

 It is not like soot, which might leave a black mark on your face 

 or clothes. The spray, if it fell on your skin or clothes, could do 

 you no harm, or at least infinitesimal harm. It is not a 

 poisonous liquid, as cattle can drink it. If it fell on trees or 

 grass, except in large quantities, which would not be the case, it 

 would not burn them. Pollution of air is not objected to unless 

 it be in great excess ; indeed, we all pollute the air to our neigh- 

 bours' and our own disadvantage. We send out gases and 

 smoke from our chimneys, which find their way to our neigh- 

 bours' carpets and curtains and clothes, and we put out the foulest 

 of gas — viz. sewer gas — daily and hourly from the ventilating 

 pipes of our modern house drains, and many of our factories, 

 electric light stations, &c., pass out gases which individually 

 one would say would be sufficient to affect a whole city. There 

 are many physical reasons which make the great difference on 

 the harmless nature of air pollution from water pollution, and 

 that is the cubic capacity of the polluted substance. 



In the case of air the air stream is measured in cubic miles, 

 whereas the water stream is a matter of cubic feet ; again, the 

 water flows in one fixed channel, whereas the wind and air 

 stream is constantly varying ; again, water pollution is worst 

 just when it is put into the river, whereas air pollution is spread 

 over a large area and is thoroughly mixed up before it comes 

 down, possibly one mile or two "miles from where it issued from 

 the chimney. 



Again, it may be said that even supposing the spray be harm- 

 less, yet it would be very disagreeable to be subjected to a fine 

 rain or Scotch mist when near the distillery. Let us consider a 

 distillery sending out four gallons per minute. An ordinary non- 

 condensing engine uses 20 lb. of water per H.P. per hour, so 

 that the quantity discharged from the top of the chimney is no 

 more than what is sent out from a steam engine (high pressure) 

 of 120 I.H.P., and we know from experience that this can be 

 discharged without being felt, and in most weathers even be- 

 coming invisible lOO feet away. If it were practicable to re- 

 duce the effluent to a state of fine division as fine as the globules 

 of the so-called white steam, and emit it from the top of a 

 chimney, the solution of the matter would be found at once. 

 It does not at present either appear practicable to reduce the 

 effluent to such a fine state of division, nor fortunately is it 

 necessary to do so, as experiment shows that ordinary sprayed 

 particles are rapidly evaporated and absorbed. Take a spray 

 such as barbers use, and spray it from a height of 5 feet in a 

 still atmosphere, and measure the quantity evaporated in its 

 descent. It will be found that at least i/8th has been lost. Do 

 the same at 10 feet, and it will be found that i/4th is lost. 

 Theory points to very rapid evaporation, as the particles get 

 small as the surface becomes rapidly large in comparison with 

 the cubic capacity of the spheres. Another good example of 

 rapid evaporation and absorption by the air is to use the spray 

 over a piece of glass. In ordinary weather only a very 

 short space of time renders the sheet glass quite dry again. 

 These two experiments, and our experience of the discharge 

 fron^ steam engines pointing to this, that instead of experiencing 

 a mist or fine rain, the particles would be so minute and so wide- 



NO. 1 50 1, VOL. 58] 



spread that no one might suff"er any inconvenience, indeed 

 might be quite unconscious of the fact that the spraying was 

 going on except from seeing the white steam mist issuing from 

 the chimney of the distillery. 



Coming now to a more practical view as to what would be 

 necessary to obtain the desired eff'ect, and trials lead to this, 

 that for a discharge of four gallons per minute it would be 

 necessary to have a pump to pump up this small quantity, also 

 an air pump to pump about forty times the volume liquid, a 

 5- H.P. oil engine with air pump attached, such as is used in 

 lighthouses for supplying the air blast to fog signals, being 

 ample. The necessary length of pipes leading up to the spray- 

 ing apparatus with a number of nozzles, and above all a high 

 point of discharge, completes the arrangement. 



The height of discharge is evidently one essential Oi 

 success. The height will vary with the amount of the 

 effluent, and whether the works be situated on a moor, 

 near a town, or in a cleft in the hills, or among high trees. 



The increase in the velocity of the wind with height is an im- 

 portant factor. In measuring the velocity at 50 feet, 100 feet 

 and 200 feet, we find a great increase with height, so that 

 instead of a point of discharge of 200 feet being only capable of 

 doing twice what a height of 100 feet will do, as one might at 

 first suppose, yet a little consideration will show, as the area is 

 a measure of the degree of dispersion, that it will disperse 

 successfully much more. In fact whereas 100 feet might dis- 

 charge one gallon, 200 feet might discharge eight gallons per 

 minute. It would appear, therefore, that to attempt to deal 

 with the effluent by spraying at a low level, as has been in some 

 quarters suggested, is simply to court failure. The point of 

 discharge must be high, but "how high" is a matter which at 

 present is unknown ; nor, indeed, can it be definitely fixed, as 

 has been pointed out, each individual work requiring special 

 consideration of the circumstances. There is one other point 

 that requires to be considered in connection with the whole 

 matter, and that is compensation for water abstraction. At 

 present distillers use the water, and what is not sent off" as 

 whisky is returned to the stream. But in the case of carrying 

 the effluent to the sea, compensation would require to be given 

 to the stream by means of reservoirs, and with the spraying 

 apparatus a complicated question would arise as to how much 

 really found its way back into the water-courses of the particular 

 drainage area. This is largely a legal question, but it is not 

 clear how the spraying process could differ from the discharge 

 into the atmosphere of an ordinary steam engine, and so it would 

 appear that water compensation for the stream was with this 

 .system unnecessary. C. A. Stevenson. 



The Nature and Habits of Pliny's Solpuga. 



I HAVE never seen one of the Arachnoids in a hive, but have 

 received them several times from trustworthy bee-keepers who 

 have found them in the hives "killing and eating the bees." 

 Other insects do the same thing, especially Formicids and 

 Mutillids. Of course the latter, with more chitine, are better 

 fitted to resist the attack of the bees than are the soft-bodied 

 Datames. It may be that these Solpulgids have some protective 

 scent that makes their entrance to .the dark recesses of the hive 

 safe. A. J. C. 



Claremont, Cal., June 23, 



THE VACCINA TION BILL. 

 T N connection with the recent discussion on the 

 -^ vaccination question, nothing strikes the inquiring 

 observer more than the shortness of the collective 

 memory 01 a people, unless, indeed, it be the fact that 

 people are easily led by any small knot of agitators 

 who will shout loudly enough and asseverate with 

 sufficient force and frequency. 



That this is true not only of what may be called the 

 masses, but also of their selected representatives in the 

 House of Commons, is evident from what has recently 

 transpired in that august assembly. The career of the 

 Vaccination Bill has been marked by many stormy 

 passages and by very varying fortunes, and now that it 

 has passed through its first stage, there appear to be 

 few who are even partially satisfied. This is a result 



