1 873.] A Solution of the Sewage Problem. 55 



all the substances which had shrunk to their least dimensions 

 must expand according to their various degrees, — not greatly, 

 indeed, so far as any small quantity of matter is affected, 

 but to an important amount when large areas of the moon's 

 surface are considered. Remembering the effects which 

 take place on our earth, in the mere change from the frost 

 of winter to the moderate warmth of early spring, it is 

 difficult to conceive that such remarkable contraction and 

 expansion can take place in a surface presumably less 

 coherent than the relatively moist and plastic substances 

 comprising the terrestrial crust, without gradually effecting 

 the demolition of the steeper lunar elevations. When we 

 consider, further, that these processes are repeated not year 

 by year, but month by month, and that all the circumstances 

 attending them are calculated to render them most effective 

 because so slow, steadfast, and uniform in their progression, 

 it certainly does not seem wonderful that our telescopists 

 should from time to time recognise signs of change in the 

 moon's face. So far from rejecting these as incredible, we 

 should consider the wonder rather to be that they are not 

 more commonly seen and more striking in their nature. 

 Assuredly there is nothing which should lead our telescopists 

 to turn from the study of the moon, as though it were hope- 

 less to seek for signs of change on a surface so desolate. 

 Rather they should increase the care with which they pursue 

 their observations, holding confidently the assurance that 

 there are signs of change to be detected, and that in all 

 probability the recognition of such change may throw an in- 

 structive light on the moon's present condition, past history, 

 and probable future. 



IV. A SOLUTION OF THE SEWAGE PROBLEM. 



fHE treatment of sewage has long been an important 

 question of Sanitary Reform. But the discussion 

 involves a second question equally momentous, — that 

 is, its utilisation, which is by no means implied in mere 

 deodorisation or disinfection. A forcible illustration of 

 this is found in Lord Palmerston's celebrated definition — 

 " Dirt is matter in the wrong place." The offensive ele- 

 ments contained in sewage are in the wrong place when 

 sent in to the river, but are in their right place when they 

 are separated from it, and reserved, like the farmer's manure 



