56 



SCIENCE. 



[Vol. IX., No. 207 



her displacement by projecting or withdrawing 

 telescopic chambers in her sides, instead of pump- 

 ing water into or out of ballast tanks, the method 

 usually followed in similar boats. The boat is 

 spindle-shaped, 60 feet long and 8 feet in diameter 

 amidships, built of |-inch steel, and is propelled 

 by aa electric motor of 45 horse-power, current 

 being furnished by storage batteries. 



LETTERS TO THE EDITOR. 



*t* Correspondents are requested to be as brief as possible. The 

 writer's name is in all cases required as proof of good faith. 



Popular science. 



It is often very popular indeed. Here is an article 

 on the Yoices of animals by Detler von Geyern (who- 

 ever he is), from Ueber Land und Meer, translated for 

 the Popular science monthly, January, 1887, written in 

 the good old traditional vein, quoting what anybody 

 has said on the subject in a wonder-mongering way, 

 as if every thing said and written must be true. 

 And Herr von Geyern himself says, " Fish can pro- 

 duce no sound in water, because air is lacking 

 as a medium to propagate the waves of sound ; 

 and yet we incline to the belief that water itself may 

 admit of forming some kind of sound-waves which 

 the fish may be capable of exciting, and which will be 

 experienced and comprehended by other fish ; " and 

 he adds, " As far as we are concerned, of course, fish 

 will remain mute," etc. — as if between fifty and a 

 hundred species of fish are not known to make 

 sounds, many of which have been described and ex- 

 plained by naturalists ; and as if water and every 

 other elastic medium were not well known as propa- 

 gators of sound, often better than air, — a factfamiliar 

 to boys, who hold their heads under water, while 

 bathing, to hear the loud sound made by the striking- 

 together of two stones under water in the hands of a 

 companion at a little distance. H. W. P. 



Grinnell, lo., Jan. 14. 



The natural method of language-teaching. 



I read with much pleasure the recent article of 

 Professor Carpenter on the natural method of teach- 

 ing languages. Such articles are in the direct inter- 

 est of truth, and therefore of science ; for the more 

 the claims and achievements of the teachers of these 

 methods are scrutinized, the more evident their 

 weakness becomes. Every intelligent teacher knows 

 that there is little if any thing really new in any of 

 these methods, and every good teacher of languages 

 has employed several, if not all, of their varieties and 

 sub-varieties, each of which is superior to the others 

 in the opinion of their self-styled inventcjrs. We are 

 safe in assuming that the natural method of learning 

 a foreign language is at least as old as the time of 

 Cain, for it is both probable that he learned the 

 language of the people of Nod, and that he used 

 neither grammai- nor dictionary. 



I believe, that, in the main, great improvements 

 have been made recently in the teaching of lan- 

 guages, but not greater than, or even so great as, in 

 the natural and physical sciences, as they are com- 

 monly called. For some reason the teachers of the 

 last two have either been more modest in proclaim- 



ing their progress, or they have been more generally 

 aware that they are only employing methods that the 

 best teachers in these departments, as in all others, 

 have been using to a greater or less extent ever since 

 the birth of science. 



Several years ago I took considerable pains to exam- 

 ine, both at first-hand and at second-hand, the claims 

 of several of the most widely known teachers of 

 natural methods as applied to foreign languages. I 

 then made some statements that agree almost verbatim 

 with those made by Professor Carpenter. In spite of 

 the well-established fact of every-day experience, 

 that the adult is able to retrace but very imperfectly 

 the psychological experiences of his early years, we 

 are told that all persons, no matter how old, should, 

 if desirous of learning a foreign language, proceed 

 exactly in the same way that they learned their 

 mother-tongue. This is the inductive method run 

 riot, while experience and generalization count for 

 nothing. To me the best refutation of the claims 

 of most teachers of natural methods lies in the fact, 

 that, while professing to be able to teach us to 

 " read, write, and speak their vernacular correctly in 

 an incredibly short time," I have not yet found one 

 or heard of one who spoke English more than pass- 

 ably, even after years of practice. Shall we say, 

 ' Physician, heal thyself ' ? or shall we excuse their 

 shortcomings for the reason that ' physicians never 

 take their own prescriptions ' ? Chas. W. Super. 

 Athens, O., Jan. 16. 



Stereoscopic vision. 



The letters in the last two numbers of Science (ix. 

 Nos. 204, 205) in relation to stereoscopic vision lead 

 me to ask if any of your readers have ever tried the 

 experiment of viewing a stereoscopic picture with the 

 naked eye, and, by changing the focal distance, or 

 visual angle of the eyes, so adjusting them, while 

 looking at the picture, or, more properly, the two 

 pictures, that the full stereoscopic effect is produced, 

 and all parts of the picture stand out distinct, and in 

 as bold relief as when seen through the two glasses. 

 The first effect of the change of the visual angle, 

 from the paper on which the pictures are imprinted 

 to a more distant range of vision, is to double the 

 number of the pictures, four now coming into view, 

 The two inner ones overlap more or less, and slide 

 over each other to right and left, as the visual angle 

 undergoes alteration, until finally, when the proper 

 adjustment is reached, the two pictures coincide in 

 all their parts, coalescing, as it were, like two drops 

 of water or two globules of quicksilver when they 

 meet and run together. And now there are three 

 pictures in view, and the eyes may be turned about 

 from one point to another, and any part or particu- 

 lar object in the picture minutely inspected in any 

 one of the three copies. The central picture is the 

 most clear and distinct, being held in view by both 

 eyes, while the two outer ones are respectively visi- 

 ble to only one eye. W. W. Anderson, M,D. 

 Stateburg, S.C, Jan. 13. 



An electric ball of fire 



In the summer of 1881 it was my good fortune to 

 observe some electrical phenomena in the way of 

 ' globular lightning,' which differ, I think, in some 

 respects, from any other case on record. It consisted 

 of a ball of fire which rolled down an iron water- 



