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classification, elevate the vegetative organs at the cost of the reproductive ones. I reply I am merely applying principles already adopted by botanists throughout the world. They are those of DeCandolle, of Endlicher, of Lindley, of Brongniart, and of Balfour. These writers, in common with most others, recognise primary distinctions that are purely vegetative. Not only are those which separate vascular from cellular plants of this character, but the further ones of exogens, endogens, acrogens, and thallogens are of the same nature. The fact of the closest resemblance of the inflorescence, and of the formation of the embryo in the embryo-sac in the two groups, does not prevent the separation of the flowering plants into exogens and endogens. Turning from the phanerogamous to the cryptogamic plants, we find that nearly every writer of importance adopts vegetative features as the basis of his classification. DeCandolle divides his Acrogens into those which have and those which have not vascular tissues. Endlicher's primary term Cormaphyla refers to a vegetative feature, viz., the possession of a stem, whilst his secondary divisions of Acrobrya, Amphibrya, and Acramphibrya all refer to the mode of growth and not to fructification. Lindley again distinguishes his flowerless plants according as they are acrogens or thallogens; whilst Balfour characterises them primarily as acrogens or cormogens and thallogens. In thus dwelling upon the vegetative element of the cryptogams, I am merely treading in the steps of nearly every writer of note who has written on these subjects. So much, therefore, for the primary point.

In many of the discussions which have taken place, my opponents have made the mistake of supposing that I was trying to prove these fossil coal-plants to be dicotyledonous exogens. Whereas what I have throughout contended for is that they are true cryptogams with an exogenous woody axis. Mr. Carruthers says, "The plants were true cryptogams, and in their organisation agree in every essential point with the stems of Lycopodiacea" (NATURE, p. 337). With this I of course agree, but I contend that we must interpret the lower forms by the higher and not the higher by the lower. In Carboniferous ages, these plants became superb forest trees, and consequently their stems attained their full development, growing year after year, from their almost microscopic condition when they burst from a microscopic spore, until they became stately trees, such as were revealed at Dixon Fold, and such as are illustrated by specimens now in the Manchester Museum. In the course of their magnificent development the stems were gradually fitted to sustain an enormous weight of branch and foliage. This was done by the development, within those stems, of a vascular woody cylinder, which grew thicker year by year; such thickening being the result of additions to the exterior of the previous growths. We here come to a definite issue. Do my opponents intend to deny the existence, in these arborescent carboniferous plants, of these thick ligneous cylinders, or to dispute that they grew in the way described? I think they cannot possibly contemplate doing so. Dr. M'Nab says botanists are agreed in this, that " Lepidodendra and their allies are closely related to other Lycopods. Now we know that the Lycopods, like the Ferns, have closed fibrovascular bundles; bundles which can only grow for a certain time, and then, all the cambium being converted into permanent tissue, growth must cease." The italics in the preceding paragraph are my own. With the above remark, so far as Ferns are concerned, I thoroughly agree. The facts so correctly stated by Dr. M'Nab constitute one of the fundamental bases of my proposed classification. The vascular bundles are closed in all the small ferns, and they remain equally so in the Cyatheas and other arborescent ferns which attain to stately dimensions. The development of this type into a lofty tree has not materially modified the structure of the stem which recurs in the most dwarfed species. But when Dr. M'Nab applies the above general statement to the Lycopods,

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facts do not sustain him. The huge lepidodendroid carboniferous plants give it a direct contradiction. They have not closed vascular bundles, and their growth did not cease after a limited time, but was obviously continued, being sustained by a cambium layer, until the plants assumed the magnificent dimensions which their fossil remains now exhibit. That the large vascular cylinder of the fossil forms is a development of what is seen, not only in Lycopodium chamaecyparinus referred to by Dr. M'Nab, but in every one of the numerous Lycopods of which I have examined sections, I have never denied. Quite the contrary. But I repeat we must interpret the significance of the least developed form by that which is most developed. Consequently we must regard the irregular vascular bundles which exist, commingled with cellular tissues, in the axis of each living Lycopod, as a degraded wood cylinder, whose nature can only be understood by reference to what it once was when its parent tree was one of the glories of the primæval forest. The race as a whole has become degenerate, and the stem being no longer called upon to sustain a lofty superstructure, its structure has become equally degenerate. I will not enter in detail into the question of the nomenclature of the various parts of these exogenous cryptogamic stems, but reserve that subject for some other occasion, after my detailed memoirs now in the hands of the Royal Society have been published. I will merely express my conviction that Mr. Carruthers, who differs widely from me on the subject, assumes the very question in debate between us.

He holds that we can draw no parallel between the conditions existing in the stems of Cryptogams and those of Phanerogams. This is precisely what I contend we can do, and I trust to be able, as my self-appointed task proceeds to its conclusion, to demonstrate to the botanical world that I have abundant reason for so doing. This is a question wholly resting upon facts, and until those facts are fairly before the world, I object to the adoption of any a priori conclusion on the subject. Consistently with his views Mr. Carruthers objects to my applying to the stems in question such terms as medulla and medullary rays; especially objecting to the application of the term medulla to a structure containing vessels, i.e., a vascular medulla; but Nepenthes has a vascular medulla, as well as some other phanerogamous plants, and no one presumes to deny the medullary character of such a tissue, because it happens to have vessels in it. The medullary character of the structure does not rest upon the basis of its being wholly devoid of vessels, neither does their occasional presence militate against its being a medulla.

In the preceding remarks I have confined myself substantially to the task of making clear the points at issue between my opponents and myself. In adopting my views of the exogenous structure of the stems in question, I am but following in the steps of some of the ablest of living botanists. M. Adolphe Brongniart, than whom no higher authority can be named, not only adopts the exogenous theory, but is so deeply impressed with its force that he denies the probability of many of the plants in question having been cryptogamic. He places them amongst the gymnospermous exogens. Recent events, however, have shown that though exogenous they are true cryptogams. How absurd, then, to apply to such stems the term acrogen or acrobrya! This controversy must be ultimately settled by the logic of facts, not by vague opinions, and to these I confidently appeal. The details of my proposed classification can only be discussed when all the facts are before the public. When this is the case, I hope to show that my proposition not only does no violence to the true affinities of living cryptogams, but that, in bringing the ancient and modern types into a philosophical relationship, it accomplishes what, under existing systems of classification, it is impossible to do.

W. C. WILLIAMSON

METEOROLOGY IN AMERICA *

II.-ORGANISATION OF THE UNITED STATES SIGNAL whole people of the country, the press, both Houses of

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It may be added that, without distinction of party, the Congress, and the President, have earnestly sustained and advanced this important branch of the public service. The military system is one of the most valuable features in the constitution of this Signal Service for the benefit of Commerce. The advantages of having the whole corps of weather observers in the army are manifest and manifold. Each observer feels the responsibility of a sentinel at his post, which begets in him a sentiment of devotion to duty the strongest of which men are capable, and which has often led the soldier to imitate the example

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of the Roman guard at Pompeii, who, after nearly eighteen centuries, was taken from its ruins in his martial position, showing that he had not fled before the molten flood from Vesuvius. Experience has proved what the sense of the Government originally suggested, that observations would be most punctually and scrupulously taken at the different stations by men accustomed to the discipline and obedience, even in minutest details, of army subalterns. They are required to work out no difficult problems in meteorology, but simply to observe and record the indi*We are again indebted to Harper's Weekly for the continuation of the article by Prof. Maury, and the woodcuts which we reproduce this week.

cations of their instruments, and to transmit the same without delay or inaccuracy. In doing this work, they have become by tri-daily practice as expert and exact in reading the glasses as any of our veteran scientific menindeed, as much so as a Fitzroy or a Leverrier could be.

Regarding the Signal Corps scattered through and over all parts of the country, we may compare it to a regiment on drill three times a day, the telegraph instantly revealing to the commanding officer, General Albert J. Myer, at Washington, the slightest failure in any observer.

By this now widely spread and magnificently organised system, the United States army, engaged under the chief

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habits of exactness acquired by the Signal Corps in time has a profession at all times lucrative to himself wherever the telegraph, and to become a skiltul operator. He thus of peace will be of the greatest value to the army in time he may be afterwards thrown. The training, skill, and At Fort Whipple, Virginia, every man is taught to use

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FIG. 5. WAR DEPARTMENT WEATHER MAP (SIGNAL SERVICE, U.S.A.), SATURDAY, APRIL 8, 1871, 7.35 A.M WASHINGTON The Numerals denote: 1st, the State of the Thermometer; and, that of the Barometer; and, 3rd, the Force of the Wind.

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of war. The telegraph is capable of indefinite utilisation. General Von Moltke, it is well known, conducted the late operations of the German army on the battle-fields of France sitting in the rear with his map before him, and his telegraphic operator at his side, keeping him in communication with all parts of the field. It has been frequently said by distinguished military men that the telegraph will be one of the most effective weapons in any war that may now occur How necessary for the Government to keep up the efficiency of such a corps as that of which we have spoken!

As the organisation under General Myer now exists, the President and Secretary of War have a responsible military man at every important post in the country. If a warlike expedition appears on any part of our coast, causing a panic or stampede, there may be a thousand wild rumours of frightened message-senders. The Government, however, is in the receipt every eight hours (and can be in the receipt every hour if it wishes) of a reliable

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FIG. 6. SECTION OF GREEN'S STANDARD BAROMETER

message from its own agent, who reports on his responsibility what he saw and knows to be true; and this observer will not leave his post until ordered to do so. As a mere Government police, therefore, the Signal Corps would be worth to the nation far more than it can ever cost, even if its operations should be more widely extended, as will speedily be done.

Each sergeant is sent to the Signal Service school for instruction at Fort Whipple, Virginia, where he is immediately supplied with Loomis's " Text-book of Meteorology," Buchan's "Hand-book of Meteorology," Pope's "Practical Telegraphy," and the "Manual of Signals for the United States Army," together with all the instruments necessary for practical instruction. The books he must thoroughly master. He is required to cite once daily didactically, and to practise a certain time with the instruments. He is required to remain under tuition until considered by the instructor competent to take charge of a station and perform the necessary duties, when he is

ordered before a board, consisting of three army officers, for examination, when, if considered incompetent, he is returned to Fort Whipple for further instruction and practice.

If, after a rigid examination, he is found capable, he is assigned to a station, and the necessary stationery and instruments furnished him (the latter consisting of the barometer, thermometer, hygrometer, anemoscope, anemometer, and rain-gauge), and instructions to make three observations daily, viz., at the time corresponding with 735 A M., 4.35 P.M., and 11.35 P.M. Washington time, so that every observer at each station should be reading his instruments at the same moment, and in the following order, viz, Ist, barometer; 2nd, thermometer; 3rd, hy. grometer; 4th, anemoscope; 5th, anemometer; and 6th, rain gauge.

In addition to the duties discharged by the officers of the Examining Board, Colonel Mallery, A.S.O., has the general charge of the very large correspondence of the office; Captain Howgate has charge of the statistics and all observations of the service; and Lieutenant Capron has the difficult post of instructor of sergeants at Fort Whipple.

Where a single person has been required to do the work of a station, receiving full reports from all stations, the labour occupied twenty hours out of the twenty-four. But the rule now adopted is to provide each station with two men-one a sergeant in charge and the other a private soldier as assistant. The observer stationed on Mount Washington has been alone on the mountain most of the time, and always responsible for the work.

In addition to a number of officers who form the Board of Examination, General Myer is also ably assisted by Major L. B. Norton, the property and disbursing officer of the Signal Service.

Prof. Cleveland Abbé, long known as an officer of the Cincinnati Observatory, and as an eminent meteorologist, is employed chiefly in the work of making out the daily synopsis of the weather, and deducing therefrom the weather probabilities," which are given to the public by telegram through all newspapers desirous of furnishing them to their readers.

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To the conspicuous ability of all of these officers is attributable the success of the enterprise.

The ordinary barometer in use by Signal Office observers is that of Mr. James Green (the well-known scien tific instrument maker of New York)-an instrument adopted by the Smithsonian Institution, and also by the American navy, as the most perfect to be obtained.

This barometer has its cistern furnished with a small glass index, which shows when the mercury is at the right height in the cistern. This is adjustable by a screw which works through the bottom of the instrument against the flexible bottom of the cistern. The instrument is ready for use when the mercury touches the little V-shaped index in the cistern. So simple and complete is this barometer that any one can use it, and it ought to be in the hands of all business gentlemen, and all who are inte rested in watching the mutations of the weather.

Latitude and longitude on the earth's surface mark very conspicuous differences in the mean barometrie pressure, as will be seen by a study of the Isobarometric Chart for the United States, which we gave last week.

The barometer has a slight fluctuation also under several influences. It rises when the moon is on the meridian in some places. It has a diurnal oscillation, amounting on the equator to more than one tenth of an inch, but in the latitude of New York to only oog inch, the greatest height being about ten A.M., and the least about four P.M. The nocturnal variations are much less. In the latitude of Philadelphia and New York the northeast wind causes another variation of one-fourth of an inch, due to the meeting of two atmospheric waves giving a still higher wave, and hence a higher barometer. There

is also the variation due to the height of the observer's station above the sea. This is, of course, of the first importance. The other fluctuations are comparatively unimportant, and do not blind an observer to those ominous fluctuations which precede the storm, the tornado, and the hurricane. The oscillations which indicate a storm are very marked. The tornado which recently ravaged St. Louis was preceded by a gradual fall of the mercury in the barometer, for thirty hours previous, of an entire inch. At Boston, within thirty-seven years, the barometer has ranged from 31*125 inches to 28'47 inches, the difference being 2655 inches. At London it has ranged through more than 35 inches; but in the tropics not so much. During the passage of a cyclone the mercury oscillates rapidly. The most noticeable fall occurs from four to six hours before the passage of the storm centre. This fall is often over an inch, and sometimes two inches.

Great changes are usually shown by falls of barometer exceeding halt an inch, and by differences of temperature exceeding fifteen degrees. If the fall equals one-tenth of an inch an hour we may look out for a heavy storm. The more sudden the change the greater the danger. But it is too often forgotten that the fall of the mercury is a forewarning of what will occur in a day or two, rather than in a few hours.

A variation of an inch is certain to be followed by a tornado or violent cyclone. In the tropics "the glass" has been known to show a fall of more than an inch and a half in one hour!

The following guides in predicting weather changes are selected from the "Barometer Manual" of the London Board of Trade, and are suggestive :

I. If the mercury standing at thirty inches rise gradually while the thermometer falls, and dampness becomes less, N.W., N., or N.E. wind; less wind or less snow and rain may be expected.

11. If a fall take place with a rising thermometer and increasing dampness, wind and rain may be expected from S.E., S., or S.W.; a fall in winter with a low thermometer foretells snow.

III. An impending N. wind before which the barometer often rises may be accompanied with rain, hail, or snow, and so forms an apparent exception to the above rules, for the barometer always rises with a north wind.

IV. The barometer being at 29 inches, a rise foretells less wind or a change of it northward, or less wet. But if at 29 inches a fast first rise precedes strong winds or squalls from N.W., N., or N.E, after which a gradual rise with falling thermometer, a S. or S. W. wind will follow, especially if the rise of the thermometer has been sudden. V. A rapid barometric rise indicates unsettled, and a rapid fall stormy weather with rain or snow; while a steady barometer, with dryness, indicates continued fine weather.

VI. The greatest barometric depressions indicate gales from S.E., S., or S.W.; the greatest elevations foretell wind from N.W., N., or N.E., or calm weather.

VII. A sudden fall of the barometer, with a westerly wind, is sometimes followed with a violent storm from the N.W., N., or N E.

VIII. If the wind veer to the S. during a gale from the E. to S.E., the barometer will continue to fall until the wind is near a marked change, when a lull may occur. The gale may afterward be renewed, perhaps suddenly and violently; and if the wind then veer to the N.W., N., or N.E., the barometer will rise and the thermometer fall.

which may influence the barometer to the extent of two inches. These causes, separately or conjointly with the temperature, produce either steady or rapid barometric variations, according to their force.

PRESENT OPERATION OF THE SERVICE

Although the Signal Service is yet in its infancy, and must be patiently nursed and cherished by the people for some years before it can expect to do and discharge its full mission, under General Myer's indefatigable care and skilful management it has already achieved much good, and more than compensated the public for the expense of its establishment. Since it was instituted last summer, "the chief signal officer has," to quote the words of the New York World, "thoroughly organised and equipped a system which now embraces in its scientific grasp every part of the land from Sandy Hook to the Golden Gate of California, and from Key West to the Dominion of Canada.”

Three times every day synchronous observations are taken and reports made from the stations—one at eight A.M., one at four P.M., and the third at midnight. These observations are made by instruments, all of which are perfectly adjusted to a standard at Washington. They are also all taken at the same moment exactly, these observations and reports being also timed by the standard of Washington time. The reports from the stations are transmitted in full by telegraph. By a combination of telegraphic circuits, the reports of observations made at different points synchronously are rapidly transmitted to the different cities at which they are to be published. They are, however, all sent of course to the central office in Washington. These reports are limited to a fixed number of words, and the time of their transmission is also a fixed number of seconds. These reports are not telegraphed in figures, but in words fully spelled out. There are now about forty-five stations for which provision has been made, and which are in running order. These have been chosen or located at points from which reports of observations will be most useful as indicating the general barometric pressure, or the approach and force of storms, and from which storm warnings, as the atmospheric indications arise, may be forwarded with greatest despatch to imperilled ports.

These stations are occupied by expert observers furnished with the best attainable instruments, which are every day becoming more perfect, and to which other instruments are being added.

The reports of observers are as yet limited to a simple statement of the readings of all their instruments, and of any meteorological facts existing at the station when their tri-daily report is telegraphed to the central office in Washington.

Each observer at the station writes his report on manifold paper.* One copy he preserves, another he gives to the telegraph operator, who telegraphs the contents to Washington. The preserved copy is a voucher for the report actually sent by the observer; and if the operator is careless and makes a mistake, he cannot lay the blame on the observer, who has a copy of his report, which must be a fac-simile of the one he has handed to the operator. The preserved copy is afterwards forwarded by the observer-sergeant to the office in Washington, where it is filed, and finally bound up in a volume for future reference.

When all the reports from the various stations have been received they are tabulated and handed to the officer (Prof. Abbé) whose duty it is to write out the synopses and deduce the "probabilities," which in a few minutes are to be telegraphed to the press all over the country.

IX. The maximum height of the barometer occurs during a north-east wind, and the minimum during one from the south-west; hence these points may be considered the poles of the wind. The range between these two heights depends on the direction of the wind, which causes, on an average, a change of half an inch; on the moisture of the air, which produces in extreme cases a change of half an inch; and on the strength of the wind, the stylus, and being pressed on the upper sheet, it makes a similar mark on

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