CORRESP ONDENCE. 



699 



burned so as to transfer from seventy to 

 seventy-five per cent, of its theoretical heat 

 to the boiler, and I do not know that this 

 is the best attainable. Mr. Wahl's limit of 

 twenty-five per cent, efficiency of fire-box, 

 or, as he well terms the boiler and fire-box, 

 the " steam-generator," is therefore entirely 

 too low ; neither has he mentioned the prin- 

 cipal cause of the loss of heat in steam-en- 

 gines, viz., the low efficiency of steam as a 

 medium on account of its high latent heat, 

 a very small part of which, at best, can be 

 utilized even in condensing engines, and still 

 less in non-condensing engines. In locomo- 

 tive - engines the following statement will 

 represent a fair average performance, with 

 corresponding approximate rates of loss 

 from different causes: 



Efficiency of steam-generator 55 per ct. 



Efficiency of steam and steam-engine. 8 li 

 Efficiency of machine .55 x. 8= 4.4 " 



The low efficiency of the steam stands 

 somewhat as follows : 



Units of heat required to convert one pound 

 of water from 00 Fahr. to steam at 125 

 pounds 1 pressure 1,160 



Of which the latent heat is 865 



which can not be converted into work in 

 the locomotive-engine : neither is the differ- 

 ence 1,160865 = 295 all available; for 

 212 60 = 152 of this was required to heat 

 the pound of water to the boiling-point at 

 atmospheric pressure, and still more at one 

 hundred and twenty-five pounds' pressure. 

 This reduces to 295152=143 units, all 

 of which is not obtained from each 1,160 

 units expended, for the steam is exhausted 

 at some pressure above atmosphere to get 

 more work from the engine and to blow the 

 fire, so that we really get but about ninety 

 useful units out of 1,160 expended, or about 

 eight per cent. In best stationary engines 

 (which are to yield fifteen per cent, effi- 

 ciency) this would stand: 



Efficiency of generator, app vox... 75 per cent. 

 Efficiency of steam and engine " 20 " 



Efficiency of whole machine, .75* .20=15 " 



The twenty per cent, here in place of the 

 eight per cent, in locomotives is because 

 of expanding steam to a lower pressure 

 before exhausting, of the partial vacuum 

 ahead of piston from condensing exhaust 

 steam, and of the heated feed-water which 

 should be credited to this account of effi- 

 ciency of steam. I can not here go into 

 the experiments of M. Him, and conclusions 

 therefrom, on the beneficial influence of par- 

 tial condensation on steam side of piston, 

 but the above figures, so far as they go, 

 will nearly represent the facts of efficiency. 

 I think you will do your readers a service 

 by correcting, even in this general way, the 

 wrong impressions they may have received 

 from Mr. Wahl's figures. 



John W. Cloud. 

 Altoona, Pennsylvania, July 5, 1879. 



A WONDEKFUL PHENOMENON AC- 

 COUNTED FOR. 



Messrs. Editors. 



I see by your correspondence that there 

 is some interest taken in spiritualism. 



A case occurred in my experience some 

 fifteen years ago which, for a while, made 

 a profound impression on my mind. My 

 house is situated about three hundred feet 

 from a large church, which has a fine organ, 

 that we heard more or less, when played 

 upon. 



It was in the beginning of summer ; the 

 windows being open, myself and family 

 heard more plainly than common, as we 

 thought at first, the organ. It went through 

 a chord producing at times what is called 

 the tremolo. We soon ascertained, how- 

 ever, that these sounds did not come from 

 the organ, but from the piano which stood 

 in our double parlors. It went through a 

 chord of quite a number of the lower notes, 

 giving somewhat the sound of the organ. 

 Being myself rather skeptical in matters 

 pertaining to superhuman phenomena, I was 

 touched profoundly by these manifestations. 



Some of the more timid neighbors de- 

 clared they would not live in the house; 

 myself and family did not share these views. 

 I stated to my friends that I expected to 

 find some rational cause for this most ex- 

 traordinary phenomenon. People wanted 

 to come in droves to witness this new won- 

 der, which I did not allow. Some spiritual- 

 ists came from Boston, ten miles, to hear 

 for themselves, and declared it must be pro- 

 duced by spirits from the other world. To 

 this I could not assent, never having be- 

 lieved in spiritualism. 



The Rev. Eli Fay, Unitarian, and now 

 settled at Sheffield, England, and the Rev. 

 Dr. J. C. Bodwell, Orthodox, now dead, both 

 able, discreet men, spent with me consid- 

 erable time in investigating the cause of 

 these wonderful sounds. They examined 

 the house throughout, including the cellar, 

 without success. On one occasion one of 

 my neighbors, being present, made the in- 

 quiry, " Who have played most on your 

 piano, who are now dead ? " My answer 

 was, his own wife, now dead, and the daugh- 

 ter of one of my near neighbors. He then 

 replied, " Is it possible that Caroline's spirit " 

 (meaning his wife) " is there ? " when the 

 piano seemed to go through a chord loud- 

 er than ever before, and almost made the 

 hair stand erect on our heads. 



And so it continued for some days, until 

 one evening I sat on the front stairs reading 

 the evening paper, there being no gas burn- 

 ing in the house except in the hall, and my 

 family were out. My attention was attracted 

 to a very different sound, not musical, coming 

 apparently from the piano. I stepped into 

 the parlors still the noise continued. I 

 now lighted the gas in the parlors, when im- 



