All elevations noted in this report, or in the plans, are referred to low waterline, which is assumed at 63 feet below the high water mark of 1832, whichmark is permanently exhibited at the corner of Main and Water streets, at Cin­ cinnati . A depth of water in the river of 20 feet above low water mark isconsidered a medium stage; 30 feet is called high water; 45 feet is a flood, whichseldom occurs. A flood of the height of 1832 may not be witnessed again inone hundred years: it should therefore not be considered in the question beforeus. When the river is running so high, navigation is extremely dangerous,particularly at night. All the wharves, warehouses and lower portions of townssituated on the banks, will be under water; no freight can be discharged nortaken in; business is entirely suspended for the time: therefore boats will, ifpossible, he by in safety until the water has commenced falling.

Let us suppose the river to be 45 feet high, which is an unusual rise; thiswill leave 72 feet clear height near the centre pier. Pike, No. 7, measuring 69feet, will therefore have 3 feet to spare in clearing the bridge. But most ofthose Packets which run in the lower trade, are provided with joints for lower-ing the chimneys, for the purpose of passing the arch over the Louisville canal.By lowering the chimneys, therefore, the largest class of steamers will be ena-bled to pass the Cincinnati bridge in the highest stage of water. It has beenstated to me that the Magnolia, a boat in the lower trade, has chimneys 10 feethigher than Pike, No. 7; this steamer, however, seldom comes to Cincinnati .

The observation has been made, that for a series of years, boats have increasedthe height of their chimneys;—is it inferred from this, that no one could tellwhere they would stop ? If it was established, that the growth of chimneys wasin a direct proportion to the power and capacity of a boat, then the previousobservation would be entitled to serious attention. But fortunately, the veryreverse will be found to be the fact in future. Paradoxical as this mayappear at first sight, it is nevertheless true, and will be assented to by those whohave made themselves acquainted with the principles of the steam engine andof steam generators.

The steam engine has, in its main features, not been improved materiallysince the days of James Watt . This great engineer had investigated the natureof steam and its application to various movements so thoroughly, that he disco-vered almost all that can be discovered. He foresaw the extent to which theexpansive action of steam could be usefully applied. His calculations have beenverified by the astonishing results furnished by the working of the Cornishengines. The average effect of a high pressure engine, such as are in use onour western waters, where steam is worked under a pressure of one hundredpounds and upwards, and used expansively to some extent, does not exceedthirty millions of pounds raised one foot high, by the consumption of one bushelof coal. Now there are this day many engines at work in the mines of Corn­ wall , doing an average duty of over one hundred millions of pounds of waterraised one foot high. What a vast difference! These astonishing results havebeen denied for a number of years by those engineers in Great Britain residingout of the mining districts. It is only a few years since the fact of the superiorworking of these engines has been generally credited, and considered asestablished.

But the question may be asked, how is it possible that this great discrepancybetween the effects of steam on our western waters and those of Cornwall andother districts, has so long escaped the attention of the first mechanics of the day ?It is difficult to attempt an answer. But it is sufficient to know the fact, thatit has escaped them; and that those who are engaged in the construction ofsteam engines and of boilers, have yet avast field left open for the application of theirskill and ingenuity. If I am not misinformed, the credit of the present plan of