July 15, 1887.] 



SCIENCE. 



35 



plants, which cannot be grown under similar conditions. The 

 fact that they will grow freely in soil containing ammonia, or de- 

 composing animal matter convertible into ammonia, led to the 

 conclusion that they wanted nitrogenous food. The fact that the 

 nitrogen is not an important element of their substance at any 

 period leads me to infer that these plants are incapable of decom- 

 posing water, and consequently dependent for their necessaiy sup- 

 ply of hydrogen upon ammonia or some other compound of hydro- 

 gen more readily decomposed than water. It is well known that 

 while the nitrates of potash, soda, lime, etc., are all valuable 

 auxiliaries to farmyard manures, they are of no value as a substi- 

 tute for it. Ver)' eminent chemists have been somewhat staggered 

 at the results of their experiments in this direction ; but precisely 

 as the function of nitrogen in ammonia is to carry hydrogen, so the 

 function of the nitrogen in the nitrates is to carry potash. Whether 

 we dress the soil with nitrate of soda, Ume, or potash, the result is 

 the same. With potash salts in the soil, the addition of the nitrates 

 of soda or lime leads to a double decomposition, and the conversion 

 of the potash into nitrate. Sulphates and chlorides of these bases 

 appear to have some small value as manure, although their compo- 

 sition remains unchanged ; but in the mysterious laboratory of the 

 growing plant the nitrate of potash is resolved into its elements. 

 The potash allies itself with carbonic acid to form carbonate, or 

 with carbon, oxygen, and hydrogen in various proportions to form 

 the organates of potash (the citrates, tartrates, oxalates, etc.), so 

 important to the development of fruits. 



Whether we employ ammonia or the nitrates as manure, the 

 nitrogen is liberated in the plant to unite with oxygen, and be 

 radiated as common air. In the one case, hydrogen remains ; in 

 the other, potash. 



The current theory of nitrogenous manure appears to be based 

 on a complete misconception as to the function of the nitrogen in 

 its various compounds ; and when it is once clearly realized that 

 hydrogen is the important food-substance yielded by ammonia, it 

 will be of practical interest to determine whether this substance 

 cannot be supplied more economically by the decomposition of 

 water secioidem ariem. C. F. Amery. 



Geological Questions. 



The replies to the following questions by some of the most emi- 

 nent American geologists have induced me to ask your assistance in 

 getting a wider circle to consider them. They were framed for the 

 purpose of enabling the writer to properly represent American 

 thought on the subjects mentioned, in his report on the Archaean 

 to the American Committee in August next. Those geologists who 

 are willing to render the undersigned the valuable assistance of ex- 

 pressing their opinions on the matters involved, are requested to 

 write the letter of the question, and give the answer as laconically 

 as is consistent with a clear statement of their views. In alterna- 

 tive questions, like J or N, it will suffice to append the numbers of 

 the clauses representing their opinions. 



A. Do you agree to the suggestions contained in the report of the 

 International Committee on Nomenclature (' Report of the Ameri- 

 can Committee on the Work of the Geological Congress,' pp. 49 to 

 B, p- 57) ? Please state explicitly if you are willing to accept the 

 recommendations of the congress. 



B. Do you favor the division of the Archaean Group into a definite 

 number of systems ? If so, give their names and the order of their 

 succession. 



C. Give the horizons of non-conformability in the Archaean. 



D. Do you approve of the plan of subdividing the Archaean 

 petrographically and of omitting corresponding chronological divis- 

 ions and names .'' 



E. Should the eruptives occurring in the Archaean rocks be classi- 

 fied with the latter, or separately ? 



F. Which, if any, of the following terms is applicable in Ameri- 

 can geology, and how applied ? ' Hebridean,' ' Dimetian,' ' Arvonian,' 

 ' Pebidian.' 



G. Are there cr^'stalline rocks in, and after, the Paleozoic litho- 

 logically indistinguishable from those of the Archaean ? 



H. Are there any crystalline rocks in the Archaean which do not 

 occur later ? 



I. Is mineral constitution indicative of geological age ? 



J. Are the lower stratified crystallines : (i) of aqueous origin 

 metamorphosed partly, or wholly, by igneous action ; (2) of igneous 

 origin metamorphosed in part, or in whole, by subsequent agencies ; 

 or (3) partly one and partly the other ? 



K. Are there evidences of organic life in the Archaean ; if so, 

 where, and what ? 



L. In your opinion, is Eozoon Canadense of organic origin ? 



LL. Do you approve the European map committee's (Professor 

 Lossen's) system of coloring and classifying the eruptives ? 



M. Should Serpentine constitute one class of eruptives ? 



N. Is Serpentine, (i) sometimes, or (2) always an alteration 

 product : (3) of eruptives, (4) of sedimentary rocks, or (5) of 

 either .' 



O. What, in your judgment, is the proper disposition of the term 

 ' Taconic ? ' If employed, what are its limits, and what terms should 

 it replace ? 



P. How should the Cambrian be divided ? 



O. Are ' Menevian,' ' Ordivician,' or any other more or less com- 

 prehensive foreign names, applicable in American geology ? if so, 

 how? Persifor Frazer, 



Reporter for Archaean. 



Philadelphia, 201 South Fifth St., July g. 



The Charleston Earthquake. 



In reply to Prof. Joseph Le Conte's valued criticism (Science, x. 

 p. 22), I would say that it seems to me that the method for estima- 

 ting the depth of an earthquake-focus proposed by Mr. Hayden and 

 myself differs radically from that proposed by Mallet in the ' British 

 Association Report' of 1858. His inference that the horizontal 

 motion has a maximum value where the ' angle of emergence ' is 

 54° 44' could be true only of normal waves. It cannot be true of 

 the transverse waves. He ignores the transverse waves entirely in 

 his formula ; and the omission, I maintain, is fatal to its applica- 

 bility. He also ignores the vertical component of the normal wave, 

 which at such an angle is much more energetic than the horizontal 

 component. What proportion of the horizontal motion is due to 

 the normal waves can generally be determined at considerable dis- 

 tances from the origin when the facts upon the ground are clearly 

 manifested. But at the very localities where such a determination 

 is necessary for the application of Mallet's method the difficulty is 

 greatest. It is just here, too, that all the components, vertical and 

 horizontal, normal and transverse, blend together with such effect 

 that not one of them can be ignored without fatal error. We must 

 consider their total effect. But these motions compounded repre- 

 sent the intensity, i.e., the amount of energy per unit-area of wave- 

 front. Mallet's ' circle of greatest destructiveness ' has no real 

 existence. It is a purely mathematical abstraction obtained by 

 postulating conditions which do not have any separate existence. 



Since writing the above, I have recurred to Mallet's paper, and 

 find the following : " It is certain that in all great earthquakes the 

 real mischief and overthrow at places pretty far removed from 

 above the centre of impulse are done by the blow from the normal 

 wave, which appears to come first ; hence, the main observable 

 effects are those of the normal, and we are justified and enabled, in 

 such localities, to neglect the transversal. But within a considera- 

 ble circle of area, whose boundary is evanescent, and whose centre 

 lies at the point right above the origin, the actual effects of the 

 transversal wave are very formidable, and can never be neglected." 

 [Then why should he have suggested doing so ?] " The ground 

 beneath an object so situated, such as a house or pillar (as the 

 distance from the origin to the surface is the minimum range of 

 emergence, or shortest possible, and its energy therefore the 

 greatest), is almost at the same instant thrown nearly vertically 

 upwards by the normal wave, and at the same moment rapidly 

 forced forwards and backwards in two directions orthogonal to 

 each other ; and this combined movement, which is that called 

 ' vorticoso ' by the Italians and Spanish Mexicans, is one that noth- 

 ing, however solid and substantial in masonry, etc., can long with- 

 stand." 



It is certainly a pleasure to find Mr. Mallet reasoning so justly ; 

 but in the remarks quoted it is apparent that he is taking account of 



