304 



SCIENCE. 



[Vol. XV. No. 380 



Caisson or Tunnel Disease. 



As one of the New York members of the board of consultants 

 of St. Francis Hospital, Jersey City, J. Leonard Corning, M.A., 

 M.D., of New York, had the rare opportunity of studying a num- 

 ber of cases of that remarkable afifection known as the '"caisson" or 

 "tunnel disease," which he reported in the Medical Record for 

 May 10, 1890. The disease is an affection of the spinal cord, due 

 to a sudden transition from a relatively high atmospheric press- 

 ure to one much lower. Hence, those who work in caissons, or 

 submerged tunnels, under an external pressure of two atmos- 

 pheres or more, are liable to be attacked by the disease shortly af- 

 ter leaving the tunnel. The seizure never, however, occurs while 

 the subject is in the caisson, or, in other words, while he remains 

 under pressure. 



The chief clinical features of the disease are pain, which may 

 be relatively mild, as when confined to some portion of one or 

 more extremities, or of frightful intensity, as when it appears in 

 the ears knees, back, or abdomen; anaesthesia and paralysis, 

 usually of paraplegic type; bladder symptoms, assuming the form 

 of retention or incontinence; and, more rarely, rectal disturbances 

 (usually incontinence). 



In cases of moderate severity the patient usually recovers in a 

 few days or weeks, while in the very severe ones he gradually 

 loses strength, and eventually succumbs. Besides these extreme 

 phases of the disease, there is an intermediate class of cases in 

 ■which the patient, though grievously ill, may recover sufficiently 

 to get about with sticks, or even unassisted. In these cases re- 

 covery is, however, but partial, the subject remaining more or 

 less feeble and hypersesthetic during the remainder of his life. 



Since Triger, a French engineer, first described the characteris- 

 tic pains of the caisson-disease in 1841, the affection has several 

 times received attention at the hands of European physicians who 

 were in a position to observe it in connection with the diving-bell, 

 bridge-building, mining, and other operations requiring the use 

 of compressed air. 



In the United States several opportunities of studying the dis- 

 ease have occurred during the last few years. The most note- 

 worthy of such occasions were the construction of the St. Louis 

 Bridge in 1868, the Brooklyn Bridge at New York about the same 

 time, and the Hudson River Tunnel at a later date. 



The Inefficiency of Sand Filters. 



Drs. Frankel and Piefke of Berlin have recently made an ex- 

 haustive study on the filtration of drinking-water through sand 

 (Zeitschrift fi'ir Hygiene, No. 1, 1890). Their experiments con- 

 clusively prove, says Medical News, that the danger of infection 

 from impure water is only slightly reduced by filtration through 

 sand; bacteria passing through at all times, but in larger num- 

 bers jusc after the filter has been cleaned, and again after it has 

 been in use for some time. 



LETTERS TO THE EDITOR. 



*** Correspondents are requested to be as brief as possible. Hie writer's name 

 is in all cases required as proof of good faith. 



The editor toill be glad to publish any queries conso7iant with the character 

 of the journal. 



On request, twenty copies of the number containing his communication will 

 be furnished free to any correspondent. 



Census of Hallucinations. 



Mat I ask for the publicity of your pages to aid me in procur- 

 ing CO operation in a scientific investigation for which I am re- 

 sponsible? I refer to the "Census of Hallucinations," which was 

 begun several years ago by the Society for Psychical Research, 

 and of which the International Congress of Experimental Psy- 

 chology at Paris, last summer, assumed the future responsibility, 

 naming a committee in each country to carry on the work. 



The object of the inquiry is twofold: 1st, to get a mass of facts 

 about hallucinations which may serve as a basis for a scientific 

 study of these phenomena; and, 2d, to ascertain approximately 

 the proportion of persons who have had such experiences. Until 

 the average frequency of hallucinations in the community is 

 known, it can never be decided whether the so-called " veridical " 



hallucinations (visions or other " warnings " of the death, etc., of 

 people at a distance) which are so frequently reported, are acci- 

 dental coincidences or something more. 



Some eight thousand or more persons in England, France, and 

 the United States, have already returned answers to the question 

 which heads the census- sheets, and which runs as follows: — 



"Have you ever, when completely awake, had a vivid impres- 

 sion of seeing or being touched by a living being or inanimate ob- ' 

 ject, or of hearing a voice; which impression, so far as you could 

 discover, was not due to any external physical cause?" 



The congress hopes that at its next meeting, in England in 

 1392, as many as fifty thousand answers may have been collected. 

 It is obvious that for the purely statistical inquiry, the answer 

 " No " is as important as the answer " Yes." 



I have been appointed to superintend the census in America, 

 and I most earnestly bespeak the co-operation of any among your 

 readers who may be actively interested in the subject. It is clear 

 that very many volunteer canvassers will he needed to secure 

 success. Each census-blank contains ifistructions to the collec- 

 tor, and places for twenty- five names; and special blanks for the 

 "Yes " cases are furnished in addition, I shall be most happy to 

 supply these blanks to any one who will be good enough to make 

 application for them. Wm. James. 



Harvard University, Cambridge, Mass., May 10. 



The Winnebago County (Iowa) Meteorites. 



On Friday evening, May 9, 1890, at 5.15 p.m , standard western 

 time, a meteor was observed over a good part of the State of 

 Iowa, and is described as a bright ball of fire, moving from west to 

 east, leaving a trail of smoke which was visible for some minutes. 

 It was accompanied by a noise likened to that of heavy cannonad- 

 ing or of thunder; and many people rushed to the doors, thinking 

 it was the rumbling of an earthquake. Substantiated reports 

 have been received from Des Moines, Mason City, Fort Dodge, 

 Emmetsburg, Algonia, Ruthven, Brett, and Forest City. The 

 noise was also heard at Sioux City. Some of these places were at 

 a distance of over a hundi-ed miles from the point where the meteor 

 fell. It exploded about eleven miles north of Forest City, Win- 

 nebago County, in the centre of the nortnern part of Iowa, lati- 

 tude 43° 15', longitude 93° 45' west of Greenwich, near the Minne- 

 sota State line. The fragments were scattered over a considerable 

 surface of ground. Up to the present time, there have been found 

 a 104-pound, a 70-pound, and a 10-pound mass, and a number of 

 fragments weighing from one to twenty ounces each ; and a part 

 of the main mass of the meteorite is believed to have passed over 

 into Minnesota. The pieces are all angular, with rounded edges. 



This meteorite is a typical chrondite, apparently of the type of 

 the Parnallite group of Meunier, which fell Feb. 28, 1857, at 

 Parnallee, India. The stone is porous, and when it is placed in 

 water to ascertain its specific gravity, there is a considerable 

 ebullition of air. The specific gravity, on a fifteen-gramme piece, 

 was found to be 3.638. The crust is rather thin, opaque black, 

 not shining, and, under the microscope, is very scorious, resem- 

 bling the Knyahinya "(Himgary) and the "West Liberty (Iowa) 

 meteoric stones. A broken surface shows the interior color to be 

 gray, spotted with brown, black, and white; the latter showing 

 the existence of small specks of meteoric iron from one-tenth 

 to four-tenths of a millimetre across. Troilite is also present 

 in small rounded masses of about the same size. On one broken 

 surface was a very thin seam of a soft black substance, evidently 

 graphite (?), and soft enough to mark white paper; a felspar 

 (anorthite?) was also observed, and enstatite was also present. I 

 present a paper on this meteorite at the meeting of the New 

 York Academy of Sciences, May 12, and will give full particulars 

 at the next meeting. 



This is the fourth meteorite that has been seen to fall in Iowa. 

 The other three falls were as follows: at Hartford, Linn County, 

 Feb. 25, 1847; at West Liberty, Iowa County, Feb. 12, 1875; and 

 the great fall of siderolites at Estherville, Emmet County, May 

 10, 1879, which fall comprised over two thousand pieces weigh- 

 ing from a tenth of an ounce to four hundred pounds. 



George F. Kunz. 



New York, May 8. 



