area of 111 kilometers, or 67 miles, north and south and from 82 to 68 kilometers (61 to 41 miles) east and west.

In this system the distortion, which increases as the square of the distance from the central meridian, would be 36 times as small in the air map as in the world map, since a sheet of the air map covers only 1° of longitude instead of 6°. As, however, the scale of the air map is five times as large, the errors from this source are reduced to one-seventh of those in the world map.

In order to facilitate handling, each sheet should be cut in half, the cutting lines running east and west, each half measuring some 28 by 38 centimeters (11 by 15 inches). The two half sheets should be pasted on either side of a piece of cardboard, and should have the name and number of the sheet shown in a conspicuous manner.

The Aero Club of France have prepared, this year, three trial sheets of this map, covering the area to be used in the next military maneuvers, with a view to obtaining the remarks of the aviator officers previous to publishing a final edition.

3. AERONAUTICAL MARKS.

As has been previously mentioned, each mark shall show the approximate longitude and polar distance of the point over which the aviator is flying. The sign adopted by the committee consists of half a rectangle (fig. 2) reproducing, on a sufficiently large scale, the frame of the half sheet of the air map in which the mark lies. The sides of this frame appear as broad lines, except the side where the cut is, which is shown by a fine dotted line; thus it is easy to distinguish between the upper and lower halves of a sheet. In this frame a large black dot will indicate the correct position, on the sheet, of the mark of the ground.

The half rectangle is correctly oriented, the small sides, parallel to the meridians, being due north and south.

Two large figures, reading toward the north, will be marked on either side of this rectangle, the left one giving the number of the units of degrees of the polar distance, and the right one the number of the units of degrees of the longitude.

The combination of these two figures, forming a number easy to read and remember, will be sufficient to define the number of the corresponding sheet of the map, and to give the rough coordinates of the mark itself. In every case where confusion might exist, each of the figures should be underlined.

Owing to the absence of the digits showing the hundreds and tens of degrees of longitude and polar distance, any two marks which are 10° or a multiple of 10° apart will have the same number. The disadvantage of this would not be of great importance. For an airman to confuse two such marks would mean that he would make

an error of 10° of either longitude or latitude. In latitudes between 40° and 50° this error would amount to 1,100 kilometers (700 miles) of latitude, or from 700-800 kilometers (400-500 miles) of longitude.

In an area covering the whole of France, only the extreme points of Brittany and the Vosges will have marks showing the same numbers. Consider, for instance, the marks numbered 39 in the environs of Pau. The same number as this, on land, would not occur again nearer than points in Algeria, England, Belgrade, or Hamburg, and would not appear at all in Spain or Italy. To mistake such dissimilar countries would be practically impossible.

To determine the correct coordinates of a mark, an aviator would only have to add to the number shown the hundreds and tens of degrees of polar distance and longitude. The remainder, with an error of perhaps a tenth of a degree (or a few minutes), could be estimated by examining the position of the dot, with reference to the sides of the mark. The position of the mark could thus be estimated with an error of less than 10 kilometers (6 miles) in either direction..

4. CONCLUSION.

The initiative thus taken by France in producing an air map and establishing aeronautical marks will very probably be followed by other countries. In such a case it would be necessary to have an international agreement to give definitely the conventional signs of the air map and other details.

In May last the cartographical committee of the International Aeronautical Federation, which met in Brussels to consider such questions, adopted in principle the meridian of Greenwich as the origin of the longitudes, a scale of 1:200,000 for the air map, and for the limits of the sheets, meridians and parallels one degree apart, starting from Greenwich and the Equator, and decided that electrical power lines, which are so dangerous for airships and aeroplanes when landing, should be shown on the map.

As regards the aeronautical marks, this committee did not venture to select any one system out of the numerous ones that were proposed, and only suggested that the names of the respective localities should be marked, in large letters, on roofs, especially on those of railway stations. As many stations, however, would thus show the same name, this would be a source of error and confusion; in addition to this, the aviator would have to consult a dictionary of names of boroughs, in order to find the number of the sheet of the air map which he requires. A system of marks showing the cutting lines of the sheet concerned, together with an abbreviated distinguishing number, seems to be much more precise, significant, and certain. It is therefore to be hoped that sooner or later this system will be universally adopted.

GEOLOGIC WORK OF ANTS IN TROPICAL AMERICA.1

[With 1 plate.]

By J. C. BRANNER.

INTRODUCTORY.

In 1900 I published a short paper on the geologic work of ants in the Tropics. Since then a good many additional observations, notes, and photographs have been made, and the most important of them are here brought together in a single article.

There are many brief notes on the work of ants scattered through the writings of travelers in tropical countries, but these notes are for the most part repetitions of rather vague and sensational stories which make no claim to accuracy of statement, so that they would add little or nothing to the value of the article. No attempt has therefore been made to use such notes except in so far as they seem to afford new or important corroborative evidence. At the same time it is realized that some of the things that ants do in tropical countries are so remarkable that those who have no personal experience of them may be pardoned for regarding the stories told about them with a certain amount of suspicion. For this reason I have confined myself to my own observations and to some of our most trustworthy scientific writers, such as Bates, Belt, and Spruce, who are naturalists to be taken seriously.

The best anyone can do who has not seen the work of ants in tropical countries is to turn to what can be seen in temperate regions. But the work done by ants in temperate zones is, with a few exceptions, of no geologic importance at all as compared with that done by them in some parts of the Tropics.

The work of the ants, in so far as it is of geologic importance, consists chiefly of their nests, habitations, refuse heaps, or mounds, above ground and their burrows, tunnels, passageways, and other excavations beneath the surface, and the opening up of the soil and the subjacent rocks to the various atmospheric influences.

1 Read before the Cordilleran Section of the Geological Society of America Mar. 25, 1910. Manuscript received by secretary of the society Apr. 29, 1910. Published Aug. 20, 1910. Reprinted by permission (condensed by author) from Bulletin of the Geo ogical Society of America, vol. 21, pp. 449–496.

• Journal of Geology, vol. 8, pp. 151-153. Chicago, 1900.

In the United States we have very little evidence of ants making either underground passageways or mounds of sufficient size or extent to have attracted much attention. Indeed, it seems to be generally conceded by entomologists that the ants of the northern part of North America are not as enterprising as those farther south, or even as those of Europe. Forel seems to have found the structures of our North American ants so insignificant that he avoided speaking of them as having mounds at all. Certainly the little ant hills we have seen in most parts of the United States are too insignificant to attract the attention of geologists. In the South and Southwest they are somewhat more conspicuous, and in the semiarid portions of western Texas and in Arizona, New Mexico, and parts of California they have attracted not a little attention.

The western halves of Oklahoma, Kansas, and Nebraska and the eastern portion of Colorado are inhabited by mound-building prairie ants that are sufficiently abundant and sufficiently pugnacious to have attracted the attention of farmers and entomologists, if not geologists.1

In the Western States generally ants are more abundant than they are in the East, but a writer on the ant hills of southwestern Wisconsin says that in that part of the country he knows at least a hundred. so-called ant hills within a radius of 5 miles, and he appears to regard this number as quite striking. Their mounds, he says, are as much as 75 centimeters in diameter and 40 centimeters in height. These cases are mentioned simply for the purpose of contrasting the size and number of ant hills in a region that seems to be regarded as pretty thickly inhabited with some of the typical localities in the tropical portions of South America.

Furthermore, in the tropical parts of America ants are not the simple and easily ignored insects with which we are acquainted in the temperate zones of the earth. Save in the cities, they are almost omnipresent. To the housekeeper they are not only never-sleeping pests, but they are bold and defiant robbers or sneak thieves, as circumstances require or permit. To the planters they are veritable plagues; they destroy the growing crops as completely as if they had been burned over. They do not wipe out a field of grain in a few hours as completely as do the locust swarms of Argentina, and then disappear, but they stay with their work right alongside of the crops, and with time they destroy them no less certainly. Unlike the locusts, they do not come and depart, but they stay right in one circumscribed area all their lives. Farinha de mandioca, the meal prepared from the cassava plant, or grain of any kind and of a size small

1 T. J. Headlee and George A. Dean: The mound-building prairie ant (Pogonomyrmex occidentalis Cresson). Bull 154, Kansas Agricultural Experiment Station. Manhattan, 1908.

2 Hermann Muckermann: Psyche, vol. 9, pp. 355-360. Boston, 1902.

enough for them to carry, require to be guarded with constant care. I have known entire bagfuls of farinha de mandioca to be carried away by them. In short, the inhabitants have to be constantly on their guard against the ants, both indoors and out of doors, to say nothing of the mere inconvenience of their presence. Nor can their importance be regarded as whimsical in any sense; indeed, I am convinced that they are social, and even national, factors that are not to be ignored.

Nothing in the way of a biologic or systematic study of tropical ants is attempted in the present paper. However valuable such a study might be, it is the number of individuals, rather than the number of species, that concerns the geologists, though it is recognized, of course, that some species are much more active agents than others. We need concern ourselves with only two large orders-the true ants belonging to the Hymenoptera, and the termites, or so-called white ants, neuropteroid insects which belong to the Isoptera, and are known all over Brazil by the popular Indian name of "cupim." And nothing is attempted in the way of a study of the architecture of their nests and underground passages, save in so far as such details will give a better idea of the geologic bearing of these matters.

In studying the work of ants in the Tropics one is constantly reminded of Mr. Darwin's studies of the work of earthworms. Mr. Darwin was able to give the quantitative results of his studies; in the case of the ants, unfortunately, quantitative results have not been possible. The time occupied by them in doing a given amount of work varies so much that quantitative observations, in order to have any value, would have to be carried on upon many colonies and for a long period of time. The results given at page 316 are an attempt at quantitative determination, but it will be observed that it is not known how many individuals took part in the work or how long they were at it.

To illustrate this article especial pains have been taken to get as many photographs and sketches as possible of the above-ground structures of ants and termites, and the accompanying illustrations have been carefully made from photographs, most of them taken in Brazil. It seemed better to have the drawings made rather than to use the original photographs, in spite of the evident suspicion of exaggeration or alteration, whether intentional or accidental, to which all drawings are open. This redrawing was the more necessary because the photographs were taken hastily and under many unfavorable circumstances, and they are therefore often not good, or they are not available for reproduction as photographs. Abundant illustrations are given because it is felt that they are the most trustworthy witnesses one can put in evidence regarding the subject.

38734°-SM 1911-20