current, which, especially in flood time, carries much of the bottom deposit bodily over the bar and drops it to seaward.* At weak points of the bottom inside the bar, therefore, the upward pressure of the mud may cause a bulging up at least to the level of the bar-crest, and, perhaps, taking into account the difference in the specific gravities of the comparatively solid bar and liquid mud, even as far as the surface of the water. But this, considering the question as coming within the domain of liquid statics, would seem to be about the extreme limit to which the bottom itself could be brought up.

I have found the specific gravity of the mud flowing from the West Crater on Marindin's Lump, to be about 1.25; that from the cone on Salt Spring Island, on Northeast Pass, 1:30; while that of bar deposit from the crest of the Northeast bar, wet as brought up by the lead, was 1.75. The heights of communicating columns of these substances, if sensibly liquid, should be as 5 to 7 ; but this ratio could apply, in the case of upheaval, only so far as the difference of level between the bar and the upheaved bottom is concerned, since the latter must be presumed to be similar to the bar in its materials and structure. Should the current, however, continue to denude the crest of the upheaved mass, the rising would continue and the semi-fluid mud might finally break through, forming a mudspring, the height of whose vent above its source might finally increase to the extent corresponding to the difference of specific gravity.

The craters of mudlumps have been sounded to the depth of 24 feet, but no precautions were used to insure reaching the actual maximum depth. In the borings made for the foundation of a lighthouse on the Southwest Pass, by Mr. A. Palms (the record of which was courteously forwarded to me by the Engineer Dept.), a stratum so soft that the augur sank in it by its own weight, was met with at 58 ft., after striking, at 56 ft. a stream of water which "filled the pipe."

If then, the mud stratum, lying, say 60 ft., below the surface, be pressed by a column of deposit of 175 sp. gr., mud of sp. gr. 125 could thereby be raised 24 feet above the top of the pressing column; and this, considering the average depth of water on the bar, would account for the greatest heights to which cones are built up off the mouths.

But this is a close calculation, even if the data upon which it is based be deemed admissible in the form I have given them; and the frequency and energy with which the upheaving force acts, coupled with the fact that when a mudlump rises in the channel, so far from suffering denudation to the extent required for the breaking through of the mud, it more generally causes a silting up of the channel: seems to me to indicate that

* Humphreys and Abbot's Rept., p. 446.

a stronger force, less delicately balanced than the equilibrium of the bar, is "at the bottom" of the whole phenomenon.

This force, I think, is to be sought in the constantly increasing weight of the alluvial area above the mouths, which, itself possessing a series of mudlump vents at one time, must yet be resting in a great measure upon the still unexhausted mud stratum; as is proven by the existence of active lumps in the marshes, even though the increased resistance of superincumbent deposit as well as matted vegetation must render their occurrence there a rarity. There must still be a communication of liquid pressure between the older and newer portions of the modern delta; and this point is especially strengthened by the fact that a high stage of water in the river, which does not sensibly affect the depth on the bars, yet exerts a decided influence on mudlump activity. The river not only overflows the marshes, but loads them with additional sediment; and doubtless the increased hydrostatic pressure stops many a vent of gas, mud or water, which ordinarily discharges into the river's bed.*

Morgan's Lump, in the marsh of Southwest Pass, and Marindin's Lump on Passe à l'Outre, are now known to have been in undiminished activity for twenty-five years at least. Since that time the bars have moved gulfward a mile and a half; and one would think that, if the activity of the cones depended upon them alone, a notable difference ought to have been observed. But if the main force is a vis à tergo, while the bar serves mainly to prevent the escape of the mud to seaward, there is good cause for the secular persistence of vents that have escaped mechanical obstruction.

How far above the present mouths the head of pressure may extend, I do not pretend to conjecture. The borings at New Orleans seem to indicate that the mud stratum originally existed there also, but it would be extravagant to suppose that such pressure as that exerted in the gas wells of that city, could now be felt a hundred miles below. Yet it seems not at all unlikely, that the weight which steadily forces up the liquid mud to the top of Morgan's Lump, seven miles above the mouth, may, in part, be furnished by the enormous mass of vegetation which annually develops in the marshes, willow battures, and perhaps even cypress swamps above. Nor is the effect of gaseous pressure resulting from the constantly progressing decay of organic matter to be overlooked, although I doubt that this cause plays, ordinarily, anything more than a very subordinate part.

* I give on the plate (page 358) an ideal section, illustrating this explanation of the "origin of mudlumps."

Future observations, systematically carried out, will doubtless solve a good many of the questions here mooted; and though they may not lead to the suggestion of any means whereby the "evil geniuses of the Passes" may at present be conjured, a more precise knowledge of data, as well as of the statics and dynamics of mud, may enable us to predict at what point of advance of the mouths into the deeper water of the Gulf, their formation must cease. The Southwest Pass appears to be nearest that consummation devoutly to be wished; and were the closing of the other outlets practicable, the advance of the Southwest bar might become so rapid, as to let the youngest of the living generation witness a diminution of mudlump upheaval. Ultimately, the mouth might thus become similar to those of the Orinoco and Amazon; but until then, ceaseless activity of the river in the formation of bars and mudlumps must, in the interest of navigation and commerce, be met by an equally ceaseless and diligent effort for their removal from the channel. For while a concentration of the river current might possibly be made to maintain the needful depth upon the bars, its utmost erosive energy will be powerless against the tough, inert masses of the mudlumps.

ART. LXIII.-Observations on the Structure and habitat of the Stephanurus dentatus Diesing, or Sclerostoma pinguicola Verrill; by WM. B. FLETCHER, M.D.

THIS parasite, well known throughout the west as the "kidney worm," was first discovered, as I am informed, by Nattser, at Barra De Rio Negro in the white China hog. Although so common and injurious in this country, it had not received attention until 1870, when Prof. Verrill, from imperfect specimens, gave it a name and suggested its importance to the agricultural world.*

*Subsequent to the publication of my descriptions of this species in the Report of the Connecticut Board of Agriculture for 1870, and this Journal, vol. 1, p. 223, I found a notice, apparently of the same worm, by Dr. J. C. White, in the Proceedings of the Boston Society of Natural History, vol. vi, p. 428, Dec., 1858. Dr. White referred it doubtfully to Stephanurus dentatus Dies. or Sclerostomum dentatum Rud. (an identification that is still quite doubtful) and gave an account of its occurrence in cysts in the leaf-lard of a hog, a male and female together.

Dr. Cobbold, from information received through Dr. Fletcher, has recently published a short account of this parasite, under the same name, in the British Medical Journal (see also Nature, Jan. 26, 1871).

During the past winter I have known of several additional cases in New England. In one instance I obtained a number of fine specimens from a portion of the leaf-lard, taken from a hog raised in Litchfield county, in this state. They occupied large irregular cavities or cysts, sometimes over an inch long and partially filled with dark, disagreeable pus, in which there were numerous eggs. The cysts usually contained a male and female worm, but some contained three and others only one.—A. E. V.

This worm was brought to me in 1866, by a farmer whose hogs were dying of cholera. He had removed the lungs of several, and also cut out fragments of the liver, all of which were spotted over with little cysts containing the worms; in the bronchial tubes down to the minutest branches, they were found in abundance and in situations where no one could have placed them.

With these specimens my conclusion was that they were the Filaria bronchialis of Owen, or Strongylus bronchialis of Cobbold, and not having at this time made microscopic examination of our well known kidney-worm, the relationship between them did not occur to me at that time.

In November, 1870, while demonstrating the portal circulation in the liver of a pig, full grown, I observed a worm which measured an inch and a half in length, and in all respects resembled the kidney worm, and also reminded me of the worms I had examined five years before. Upon further dissection of the liver I found the worms not only free in the portal veins, but in cysts in various portions of the organ; also some were found in freshly cut holes, directly across the hepatic lobules. The gall-bladder was distended with a dirty, yellowish fluid, the consistency of soft boiled eggs, and although no worms were found, yet the ova were abundant, as they also were in the fluid of the cysts.

Being convinced that the worm formerly examined in the lungs was the same as the worm now found in this new locality, and finding it oviparous, I gave up my opinion as to its being a Filaria bronchialis.

From the date of this discovery, I frequented the slaughter houses and pork-packing establishments, and found the worm in most instances in the pelvis of the kidney, or in cysts in the fat around them. Four times I have found the worm in the bronchial tubes, twice in the hepatic vein and in the right side of the heart; also in cysts throughout the fatty parts of the animal.

Frequently, when no worms were discovered, the eggs were abundant in the thick mucous-looking fluid in the pelvis of the kidney. This fluid contained, besides eggs, desquamated renal tubules, or casts and oily granules.

In no instance have I found worms in an immature state, which shows that the eggs, in all probability, go through some other beast before they enter the swine, to become sexually

mature.

*

The symptoms in hogs, which are referred to the "kidnev worm," are due to a paralysis of motion in the hind legs; the

*It is quite as probable that they may hatch in water, and thus enter the hog's stomach with its drink.-v.

hog drags the hind quarters along the ground from place to place in search of his food, although it is by no means proven that the worm is the real cause, unless we be able to demonstrate its existence in some cerebro-spinal center, or some point more likely to destroy the reflex power in the cord itself.

Structure. The head and oral cavity are alike in male and female. The oral cavity is rather oval than round, and is surrounded by a hexagonal frame, each corner having a papilla and hooklet, while each side is armed with six serrate teeth.

Looking into the oral cavity, it is funnel-shaped, having three openings at the back, one of which connects directly with the oesophagus, while the others appear to connect with the water vessels.

The intestine is long and contains some pigment granules, arranged in dendritic forms, throughout its length; the whole is thrown into convolutions, and gives an almost black appearance to the worm, except when the white oviducts distended with eggs, or the seminial vessels of the male are folded over the intestine, when it has a white, mottled appearance.

The caudal extremity of the female is spindle-shaped, but has two little bursæ higher up. In the male it is formed by three-lobed bursæ, above which are two well developed flexible spi ula.

ART. LXIV.—On certain Forms of the Electrical Discharge in Air; by Prof. ARTHUR W. WRIGHT, Williams College.

IN a paper published in this Journal, May, 1870, the writer described a peculiar form of discharge between the poles of the Holtz electrical machine, worked at high tension, and without condensers. A non-luminous discharge was observed to take place over a considerable interval, with the production of a jet or brush upon the negative, and a glow upon the positive ball, and the formation in this glow of shadow-like images of objects placed between the poles. It was shown also that the discharge passed over lines having a definite form, and that they were curved so as to form arcs issuing normally from the surfaces of the poles.*

When the condensers are employed the dark discharge also occurs under certain circumstances, and exercises an important

*Faraday described the form of discharge which produces the glow, and called it the dark discharge. He also held that the inductive action between two bodies took place along curved lines, as was indicated by certain forms of the luminous discharge. (Exper. Res., 1444; 1544, et seq.; 1215, et seq.). The occurrence of the shadows, however, enables us to trace these lines of action very accurately, especially when the glow is made to take the form of a narrow ring, as is described in the paper referred to above.