He thought it right to mention that the accuracy of the descxip-Mr. Brnnton. tion in the Paper relative to the introduction of the oil-scrubber, or coke tower, had been questioned by Mr. John Calderwood, who stated that the first tower of this description, ever employed in a mineral oil factory, was intrcduced at the works of Young's Corn-, pany a t Addiewell, and was the result of experiments which he had made for Dr. Young. He admitted that another person claimed the accidental discovery, mentioned in the Paper, of the value of mineral oil as a scrubbing agent ; but he stated that this discovery was forestalled by him. Correspondence. Mr. J. N. DOUGLAS remarked that the enormous consumption Mr. Douglass.

inquired what was the gradient of the main sewer Mr. Monson. at Abingdon ? It was singular that a sewer should be constructed requiring flushing twice a week. He thought it would prove difficult to collect sewage without any surface water. He should like to know whether the sewers were fully ventilated ; whether the openings were offensive ; how many persons it was intended to make provision for to an acre of land ; what was the cost per acre of preparing the land, and what it included ; how the carriers were made ; what distance the drains were apart, and how deep? These questions were of great importance. In the inquiry now going on concerning the Thames Valley, it had been stated that the land could be prepared, 9 feet deep, a t 511 per acre. Such statements ought not to be made ; it was only by getting at the facts in connection with works already constructed that satisfactory information could be obtained. To prepare a filtration area 9 feet deep would cost, not Sll, but about $200 per acre. The cost of digging would be 5146. The soil was sandy, and it would be necessary to go down with poling boards, and perhaps close pole it ; and then there would be the cost of the roads and of the carriers. It would be impossible to make carriers by simply ploughing a sandy soil, and permanent carriers would be necessary. Altogether, he believed the cost would be $208 per acre. The Abingdon sewage was delivered on a free soil, and he presumed it would have to be prepared in a similar way to that in the Thames Valley.with reference to the cost of preparing land for the Lower Thames Valley sewage. The estimate of engineers exceeded 546 an acre all round. It would have been better if his views had been expressed at the inquiry, where he could have been crossexamined, instead of making an ex parte statement before the members of the Institution. I n Mr. Gower's Paper it was stated that the population of Abingdon was six thousand ; that at present it had no waterworks ; that the inhabitants drew their watersupply from local wells, and that it was estimated, when the population should increase to ten thousand, the volume of sewage would be 25 gallons per head per day-250,000 gallons in twenty-four hours. He wished to ask how it was that there was a much larger volume of sewage than that at the present time. He had not given the volume per head per day, but it wa0 easy to ascertain that it was over 30 gallons. Reference