May io, 1889.] 



SCIENCE. 



369 



obliged if those having opportunities of examining banks of dry and 

 fine sand, inclined at 31°, in the arid regions of the West, will re- 

 port through your columns whether they yield deep sounds when 

 ■disturbed. H. Carrington Bolton. 



Cairo, Egypt, April lo. 



Rainfall and Latent Heat. 



It is probable that no element engaged in the increase of energy 

 in storm-formation, according to ordinary theories, exceeds in im- 

 portance that of heat set free in the condensation of vapor. Pro- 

 fessor Espy was one of the first to enunciate this principle, and to 

 insist upon its entire adequacy to account for all the phenomena 

 even in the most violent tornadoes. Professor Ferrel has said, 

 " Even if any part of the atmosphere should receive such an [primi- 

 tive] impulse as to produce a most violent hurricane, friction would 

 soon destroy all motion, and bring the atmosphere to rest. Hurri- 

 canes, then, and all ordinary storms, must begin and gradually 

 increase in violence by the action of some constantly acting force. 

 , . . This force may be furnished by the condensation of 

 vapor ascending in the upward current in the middle of the hurri- 

 cane, in accordance with Professor Espy's theory of storms and 

 rains. According to this theory, all storms are produced by an 

 ascending current of warmer atmosphere saturated with moisture, 

 and this current is kept in motion by the continual rarefaction of 

 the atmosphere above by means of the caloric given out of the 

 vapor which is condensed as it ascends to colder regions above." 



Professor Mohn gives this calculation of the effect of latent heat 

 set free on Oct. 5, 6, and 7, 1844 : " The Cuban hurricane has used 

 for the moving of the air which was rushing in during those three 

 days at least 473,500,000 horse-power ; that is, at least fifteen times 

 as much as all wind-mills, water-wheels, steam-engines, locomo- 

 tives, man and animal power, on the whole earth produce in that 

 time. Whence comes this immense power? From the latent 

 heat of the vapors which rise in the middle of the hurricane, and 

 are condensed during this process. A rainfall of one millimetre 

 (.04 of an inch) per day on a circular surface eight geographical 

 miles in radius would be sufficient to produce, by the liberating of 

 the latent heat in the vapor, the force which the Cuban hurricane 

 displayed in the air-cylinder mentioned above." 



These examples will serve to show the views held by two of 

 the most prominent writers on this subject. I have examined 

 the writings of more than twelve scientists, and find that all, with- 

 out exception, emphasize the importance of this effect. Diligent 

 search has been made in all quarters for a quantitative determina- 

 tion of this effect, but without success. It has seemed of some 

 importance to make a beginning at such analysis, even though, as 

 will readily be seen, the subject is an exceedingly difficult one to 

 elucidate. The following proposition is presented : — 



There can be no considerable condensation from saherated air 

 as long as laie?it heat is set free from it. A short computation will 

 show that the condensation of a grain of water will set free enough 

 latent heat to raise a cubic foot of saturated air about seven degrees 

 in temperature. Let us imagine it to be possible to condense one- 

 seventh of a grain of moisture out of a cubic foot of saturated air 

 at 80'' without changing its temperature : latent heat would imme- 

 diately be set free, and would just re-evaporate the moisture. It 

 would seem at first sight as though this would always be the re- 

 sult, and hence that no precipitation could ever occur without the 

 intervention of some other force. At all events, the proposition 

 above seems abundantly proved. 



Suppose, however, that we try to abstract enough heat to lower 

 the temperature one degree. We shall find, that after abstracting 

 enough heat to lower the temperature one-third of a degree, and to 

 condense .HI of a grain of moisture, the rest will be needed to 

 balance the latent heat evolved by the condensation. We shall 

 then have our air saturated at 79.7°, and a precipitation of .1 11 of a 

 grain. It might be thought that this process could continue in- 

 definitely, but this is not the fact. If we inquire how the above cool- 

 ing has been possible, we find at once that it has been brought about 

 by heating the surrounding air. I think we can best see this by 

 imagining two cubic feet of air at 80", side by side and yet distinct. 

 Suppose that, instead of raising the surrounding air, all the heat 

 abstracted in cooling the first cubic foot be passed into the second. 



We shall then have one cubic foot of saturated air at 79.7°, and 

 another of unsaturated at over 80°. If, now, we mix these, we 

 shall have two cubic feet of unsaturated air at over 80°, and this 

 will need quite a cooling before any further precipitation. 



Of course, in nature no such sudden transitions as these occur, 

 but the principle seems to be the same in all cases. The results 

 following such a process are far-reaching and most important, but 

 there is no space here for dilating further upon the question. It 

 seems to me, after a most careful study of the problem, that we 

 have virtually, in an ascending current, an analogous effect to that 

 in mixing two bodies of air at different temperatures. In the latter 

 case it is admitted by all meteorologists that no considerable pre- 

 cipitation can ever occur. If this computation be true, we have a 

 most important deduction, and have apparently wiped out at a sin- 

 gle stroke one of the main-stays of theoretical meteorology as now 

 taught. I confess to great diffidence in advancing this computa- 

 tion ; but if it shall result in the development of the true principles 

 involved, and a quantitative determination of the effects in many 

 other theories now on an exceedingly unsubstantial basis, I shall 

 be only too glad to be proved in error. H. A. Hazen. 



Washington, D.C., April 29. 



"Alphabetic Law" and "World-English." 



Mr. Matthew Monroe Campbell, a retired teacher, resident 

 in Boulder, Col., has issued a series of open letters, advocating the 

 official establishment of "Alphabetic Law " in the writing of Eng- 

 lish, under the direction of a government bureau. " Alphabetic 

 Law," Mr. Campbell says, " requires (i) a single sign or letter for 

 each sound ; (2) a single sound for each sign or letter ; (3) a joint 

 name for each sign and its sound (its own sound must be the name 

 for a letter) ; (4) to ortho-graph, or right-write a spoken word, is 

 simply to change each sound in the word for a letter named after 

 it ; (5) to ortho-ep, or right-voice a written word, is simply to 

 change each seen letter back to its unseen sound ; a letter, then, 

 cannot have two values, and a letter can never be silent, for a let- 

 ter is a seen sound." 



The idea of enforcing such principles, however excellent, in 

 government printing, or by the authority of a State department, is 

 not likely .to meet with favor. The "Alphabetic Laws" are cer- 

 tainly good, so far as they go ; and I would point out that they are 

 strictly carried out in the scheme of " World-English." In the 

 latter case, however, they are not proposed for adoption in com- 

 mon orthography, but merely for facilitating the acquirement and 

 the world-wide diffusion of our language. Any thing like a proper 

 and complete phoneticism of ordinary literature is not to be looked 

 for in our day. Alex. Melville Bell. 



Washington, D.C., May 7. 



Ayrton and Perry's Secohmmeter. 



Science of April 26 contains a description of Ayrton and Perry's 

 secohmmeter, an instrument consisting of two commutators fixed 

 on the same axle. In your article it is stated that an electrolytic 

 cell will not polarize with rapidly alternating currents, and that 

 consequently the secohmmeter may be employed to measure the 

 resistance of electrolytes in a manner described. May I call your 

 attention to a paper of mine, published in 1882 in the " Transactions 

 of the Royal Society of Canada " (Sec. III. p. 21), in which this 

 method of determining the resistance of electrolytes was, I think, 

 first described } My experience in developing it showed that the 

 electrodes of an electrolytic cell do become polarized, even with 

 very rapidly alternating currents, and that consequently the method 

 which is sketched in your article cannot be trusted to give accurate 

 results. I found, however, that the double commutator, employed 

 in the manner specified in your article, was useful as keeping the 

 polarization at a very small value, and I was able to eliminate the 

 error due to it in the measurement of resistance by introducing 

 two electrolytic cells of the same section, but of different lengths, 

 into two adjacent arms of the Wheatstone's bridge, an adjustable 

 resistance being included also in the arm containing the smaller 

 cell, and by making the other arms consist of wires of equal re- 

 sistance. J. G. MacGregor. 



Dalhousie College, Halifax, N.S., April 30. 



