February 8, 1889,] 



SCIENCE. 



95 



when once ground into their seats ; and, as they are forced into 

 their seats by the pressure of steam, it is impossible for them to 

 leak. But, being heavy to lift by hand, some one invented the 

 double-balanced valve, m which the steam is pressing upward and 

 trying to open the lower of two valves, while it is pressing downward 

 on the upper one ; so that there is no trouble in opening them by 

 hand. Of course, such an arrangement must leak ; and, when 

 steam once begins to leak, it cuts its way through the crack, and 

 very soon has an open passage. 



It has not, however, been supposed that the leak was so enor- 

 mous as stated ; but the lecturer appeals to what he says are facts 

 within his knowledge, and which are easily verified any day. If it 

 is true that steamboat-engines will run the boat without open- 

 ing the steam-valves, as he says, and that it is done as a 

 practice on some East River steamers when the engine is required 

 to go slow, it is certainly most astonishing that owners should 

 permit such a state of things to continue for a day. As the lec- 

 turer says, it is a case of internal hemorrhage, where the patient 

 may bleed to death without knowing the cause. 



The lecture contains two cuts, exhibiting the single 

 puppet-valve of Watt, and the double or balanced Ameri- 

 can valve, as below. 



It is very apparent from the sketch that the double valve 

 must be leaky. The pressure upwards on the lower valve 



rious phenomenon deserves to be mentioned, and that is the attack 

 upon James Watt and his laws of steam by the Government of the 

 United States during the Rebellion, when vast sums of money were 

 expended in building steam-engines. At that time the Govern- 

 ment officially pronounced its judgment of condemnation upon the 

 laws of Watt, and published that judgment in a book, which was 

 distributed to the engme-builders and engineers of the country as 

 the authoritative decision by the United States. This absurd con- 

 clusion was reached in consequence of some experiments ignorantly 

 tried by some Government engineers, on a leaky engine on Lake 

 Erie, which, as the report showed, was using more than twice the 

 fuel to the horse-power that James Watt's engines were using. 

 What was proved by the experiment was, that such a machine as 

 that was not a good one to make forty-seven horse-power by ex- 

 pansion ; but it was assumed that it proved there was no use in 

 expansion. I quote from that book the following : — 



" ' The results obtained from this engine (that is, the Lake Erie 

 engine) are rigorously applicable to all others in which saturated 



balances the pressure downward on the upper one, and of course the 

 valve opens easily ; but unless the upper and lower valves, which 

 are rigidly separated by a column, can be fitted at exactly the same 

 distance apart that the seats are, of course they must leak, since no 

 pressure can take effect on either to force it into its seat. If they 

 could be so perfectly constructed as to be steam-tight when cold, 

 ■ the moment they are heated by steam, the expansion of the col- 

 umn must differ from that of the enclosing chest, and at once a leak 

 begins ; and when it does begin, it soon cuts away the metal. 



The lecturer takes up the present theory that great losses are 

 incurred in working steam expansively, according to the laws of 

 Watt, by what is called " cylinder condensation," which is said to 

 destroy as much as one-quarter of the steam introduced into the 

 cylinder, and to that extent neutralizing the theoretical gain by ex- 

 pansion. This hypothesis was put forward by the engineers of the 

 navy in i860, as the true explanation of a very common fact, that a 

 steam-engine does not give out power in proportion to the expan- 

 sion used. This explanation was supported by an experiment tried 

 by the United States on an engine on Lake Erie, to which the lec- 

 turer refers as follows : — 



" In the history of the development of the steam-engine, one cu- 



steam is employed in a cylinder not jacketed, and, show 

 conclusively the utter futility of attempting to realize an 

 economical gain in fuel, under such conditions, by ex- 

 panding the steam beyond the very moderate limit of one 

 and a half times; and that, if the expansion be carried 

 to three times, a positive loss is incurred ; also that if 

 measure of expansion, as high as those due to cutting off 

 the steam at ^ or /^ of the stroke of the piston, are employed, the 

 economy is considerably less than with steam used absolutely 

 without expansion.' 



" Upon that principle, the whole steam navy of the United States 

 that was built during the war was constructed. This was a tre- 

 mendous blow to progress, from which we have not yet entirely 

 recovered ; and but for the fact that the engineers of Europe have 

 since built their magnificent steamers, and carried expansion to a 

 high degree, we should have been building a navy to this day in ac- 

 cordance with this ignorance. But James Watt, for a dead man, 

 made a magnificent fight in defence of his principles ; and the 

 money and resources of the United States have utterly failed to 

 defeat him." 



In an elaborate note, an explanation is made of the way in 

 which this remarkable conclusion was reached, supported by the 

 tabulated report on which it was supposed to rest. As the table 

 shows, the " Michigan's " eiigine was run at various rates of expan- 

 sion, beginning at nearly full stroke, and running down to a cut-off 

 at one-eleventh of the stroke, — the pressure of the steam being kept 

 constant, and the revolutions of the engine kept the same, by 

 taking off resistance, — so that at full stroke the engine developed 280 



