On the Ifardenlng of Lime under TUater, 6.c. should it fail~ would be productive of no detriment to the Railway Company. I have thoroughly ennsidered the expense of such an experiment, and also the probable inconvenience that would arise out of its failur% (S ~r and supp ~ in~, the latter result, I am satislied it couhl not cost the Railway Company less than J28,000 or £10,000; and this sum may be made to appear without taking into the account many contingencies that would necessarily attend such a circumstance." The ballaslin~ and laying the rails alone costs from 42800 to £1000 pet' mite, and this charge must unquestionably be incurred in merely transforming the undulated surface to an uniform one. The embankments would require to be brought to a higher, and excavations to a lower, level; thus interfering with the whole of the bridges, over and under the railway. In short, you couht only prepare for the contingency of a failure, by e,ecting temporary bridges over the railway, throughout the ten miles, until the utility of the scheme had been determined. These and other considerations, connected with the detail of executing the railway, which it would be superlluous to enter into here, and which it wouhl be impossible to render intelligible in a report likethe present, fully convince me that it wouhl be at least rash to advise an expensive experiment on the London and Birmingham Railway, which, in any event, could only save a very small sum iu the original expenditure~ with the possibility of your not succeeding to your expectations; thus producing a result fi-aught with mischief to the undertaking generally. I feel it, however, due to Mr. Badnaii, to state that [ consider a trial upon some branch road might be made with advantage, as the adoption of his ideas would certainly be productive, in many cases, of considerable saving in the first cost~ which, in some branch roads, is nf paramount impo,'tance. l must, however, again repeat, that no saving of power could be by any possibility effccted. ROBEIt'F S'FEPHb;N SON. Note relating to the hardening of Lime under ~'ater, by the action of Carbonate of }~otas~a, ~'c., and to the hardening of Carbonate of Lime in the ~ir, by Potassa and Soda.