36 ANNUAL OF SCIENTIFIC DISCOVERY. 



ful, that precautionary measures had at once to be adopted to mitigate the 

 immediate danger; and, as a palliative, an immense amount of lime and 

 chloride of lime was put in daily. During the past summer (18-39) this 

 treatment had to be increased, and no less than one hundred and ten tons 

 of lime, and twelve tons of chloride of lime, were thrown into the river 

 daily, at a cost of 1500 per week; an expenditure which it is calculated must 

 be doubled next year, and so on until the evil is overcome. A sum of 

 20,000, moreover, was also expended during the past summer in flushing 

 the sewers, to aid in the discharge of their contents in times of extreme lo,w 

 water. 



The magnitude and importance of this growing evil have at last compelled 

 the attention of Parliament, and measures have been adopted to put an end 

 to it forever. 



The great difficulty has been to decide on the most feasible method of 

 doing the work, the necessity of which was denied by nobody. Finally, 

 however, the plan of Mr. Bazalgette, the Chief Engineer of the Board of 

 Works, has been adopted, and is already in progress. It is on a scale ade- 

 quate to the Augean labor undertaken. It consists of three gigantic main 

 tunnels, at different levels, which intercept the existing sewers at right 

 angles, thus receiving all their contents formerly empted into the river, and 

 conveying them, parallel with the banks of the river, about eight miles to 

 Barking, where an immense reservoir is to be prepared to receive them. 

 This reservoir is to be a mile and a half long, by about one hundred feet 

 wide and twenty-one feet deep, capable of containing no less than seven 

 million cubic feet, or double the average of eight hours' accumulation of 

 sewage. The object of the narrowness of the reservoir, compared with its 

 length, is to admit of its being bricked over with arches, and covered with 

 earth, so as to prevent the escape of foul gases. During the time the sewage 

 is in this reservoir it is to be deodorized, and experiments arc now going on 

 to ascertain the best method of doing this. At high tide the contents of the 

 reservoir will be emptied into the river by immense outfall pipes extending 

 to the middle and bottom of its bed, sixty feet below the surface. It is be- 

 lieved that with these precautions, the sewage, after deodorization, being 

 poured into so vast a body of water, at so great a depth, will cease to be any 

 longer an agent of mischief. 



These works are now going on with great rapidity, and in the most thor- 

 ough and profuse manner. The estimated time for their completion is five 

 years, and the expense 4,000,000 ($20,000,000). At the point where the sev- 

 eral sewers unite, the whole are enclosed in a single tunnel of the most mas- 

 sive description, powerful outer haunches or buttresses supporting the tube 

 outside, while the whole is inclosed in what may be almost termed an em- 

 bankment of concrete. More than two thousand men are at present em- 

 ployed on the work, and the whole will require about forty million bricks, 

 and many thousand tons of mortar, to complete it. So vast is the undertak- 

 ing, and so colossal are its proportions, that but for its having an important 

 and most beneficial purpose in view, it would almost remind the spectator of 

 the gigantic and meaningless works which the Egyptians seem to have cre- 

 ated, apparently only to excite the astonishment of after ages. 



ORDNANCE SURVEY OF GREAT BRITAIN. 



The National Survey of Great Britain is based upon a system of triangu- 

 lation extending over the whole country. The distances between the trigo- 



