the section at A, another cubic centimeter leaves it at B. The entering liquid carries into the section. kinetic energy ov2/2 and potential energy ogh. But it also does work on the liquid ahead of it equal to the pressure times its volume or to p, while at the same time the liquid behind does an equal amount of work upon the cubic centimeter itself in pushing it into the section; thus an amount of energy equal to p is transmitted past A through the entering liquid into the section, in addition to the kinetic and potential energy which is simply carried in. The total energy transferred past A as one cubic centimeter enters the section is thus EA =QVA2/+ogha + Pa· At the same time an amount of energy E = Qν ̧2/2+Qghв + PÅ is transferred out of the section at B; while no energy at all is transferred across the sides. The total amount of energy inside the section must, however, remain constant, for the flow is steady. Hence EA = EB and Bernouilli's Principle follows.

B

This deduction brings out the true meaning of the quantity E that is constant along a tube of flow; it represents, not the energy that is stored in each unit volume of the liquid and carried along with it, but rather the total amount of energy that is transferred past any point as each unit volume of the liquid moves past that point. The first two terms in the expression for E represent what we may call a convection current of energy, in which the energy is simply carried along by moving matter. term, p, then represents an additional current of energy that is transmitted through the liquid.

The last

If we wish, we can imagine the transmission current of energy, represented by p, to arise from a streaming through the liquid of the energy of compression. The latter energy is never quite zero, but it is always small, and so we shall have to suppose it to move enormously faster than the liquid. A similar current of energy flows along a moving belt, only there the energy moves in one direction while the matter through which it streams is moving in the opposite direction.

In gases the energy of compression need not move so fast in order to account for the transmitted stream of energy, but in this case the energy of compression contributes appreciably to the convection current as well.

This view of the Bernouilli Equation would seem to be just as useful and suggestive as any other, and it seems quite simple enough for presentation in a freshman text. As a matter of fact, examination of a number of elementary engineering books shows that most of the ideas here presented are actually to be found in one or two of those!

CORNELL UNIVERSITY

E. H. KENNARD

CAMPBELL'S DEFINITIVE UNITS

REFERRING to the paper of Dr. George A. Campbell, "A system of 'definitive units' proposed for universal use," published in the issue of SCIENCE for April 3, 1925, the writer realizes that there are many advocates of alternative universal systems of units and is therefore hesitant about entering the lists. It would appear, however, that two modifications of Dr. Campbell's proposal would be of great assistance in the practical introduction of such a system of definitive units. These are:

The retention of the C.G.S. unit of length, the centimeter, instead of the meter; and the use of the true ohm (or "practical" ohm, as Dr. Campbell calls it) instead of the international ohm. These modifications are independent of one another, and will be considered separately below.

USE OF THE CENTIMETER

It is believed that in scientific and engineering work a unit, such as the centimeter, which is smaller than most pieces of apparatus, is more convenient than the meter. It is already in such wide use and has been the basis of so many physical data that a great saving in labor and mental effort would be occasioned if it were retained. The consequence of its retention would be that the unit of force would become 107 dynes and the unit of mass would be 107 grams. This unit of force has been used in certain1 texts for a number of years. Being approximately equal to 22.5 lb., this unit is fully as convenient as the value 105 dynes proposed by Dr. Campbell, which is approximately equal to 0.225 lb. The writer recognizes that the corresponding unit of mass, 10 metric tons, is not so convenient as the kilogram, but in this connection it should be pointed out that mass in its direct aspect as a measure of inertia enters into relatively few practical and scientific calculations. Mass as a measure of the quantity of matter—that is, mass from the chemist's point of view-is a distinct idea and can continue to be measured in grams or kilograms with little confusion. These latter units of mass may be considered as derived from the large unit by the factors 10- and 10-4, in much the same way that the customary electrical unit, the microfarad, is derived from the farad by the factor 10-6. All electrical engineers are quite reconciled to the fact that the farad is an enormous unit and are not con

1 See Karapetoff, "The Electric Circuit' (1912), p. 217: "Force ought to be measured in joules per centimeter length, to avoid the old multiplier. Such a unit is equal to about 10.2 kg. and could be properly called the joulcen (= 10' dynes)."

fused by the use of the microfarad with its numerical factor of 106. As a matter of fact, the kilogram itself is too large for convenience in most scientific work. Both Dr. Campbell's proposal and that of the writer lose what was considered an advantage of the C.G.S. system, that the density of water is approximately equal to unity; so there is no choice on this point. A great convenience of the writer's proposal is that energy, power, force, mass and other quantities directly derived from them all have units larger than the C.G.S. units by the same factor 107. This would result in great convenience in referring to existing tables of physical data, since the reader would only have to decide whether to introduce this single factor; whereas with Dr. Campbell's proposal factors of 10-2, 10-3, 10-5 and 10-7 are given in his Table I, and other factors would enter with subordinate quantities, such as pressure and density. It is believed by the writer that these conveniences far outweigh the inconvenience of a large unit of mass.

USE OF THE TRUE OHM

Dr. Campbell's proposal to use the international ohm, coupled with the use of the mechanical watt, requires many of the electrical quantities to be expressed in units which have never heretofore been employed. While it is true that these units differ to a very slight degree from either the international units or the true (practical) units, nevertheless it is felt that the results would be decidedly confusing. The writer's proposal is to use the true practical electrical units throughout, which is consistent with the mechanical watt. These units are all related to the C.G.S. electromagnetic units by factors which are exactly powers of 10; so that conversion from the C.G.S. electromagnetic system would be greatly facilitated. For engineering purposes, of course, the differences between the international electrical units, the practical electrical units and the electrical units proposed by Dr. Campbell are insignificant.

The units proposed by the writer seem to require a minimum of change from existing practice and yet to have the broad advantages of definitive units as expressed by Dr. Campbell. With the exceptions of the units for force and mass and their derivatives, these units are all in wide use at present. The complete system has for several years been employed by the writer in his electrical engineering classes2 and for his own computation in fields where electrical and mechanical quantities continually occur together in a variety of ways.

In the writer's opinion, the most important con2 See L. A. Hazeltine, "Electrical Engineering," The Macmillan Company (1924).

TIME MEASUREMENTS

THE fact that a watch keeps correct time over a period of twenty-four hours is not a sufficient indication of its accuracy in the measurement of short time intervals where the second hand is used. A slight misplacement of the watch dial may cause the pivot of the second hand to be located "off center," thus causing an error of as much as two seconds in measuring an interval of twenty, or twenty-five seconds. Readings on one half of the dial will be too short and those on the other half correspondingly too long.

A similar source of error may be looked for in any dial-reading instrument where particular care has not been taken in fixing the dial position.

SCIENTIFIC BOOKS

The Story of Early Chemistry. By JOHN MAXSON STILLMAN, late professor emeritus of chemistry, Stanford University, xiii+566 pages, 512 × 82 inches. D. Appleton and Co., New York, 1924, Price $4.00.

THE amiable author of this scholarly volume (whose recent death was lamented by a host of friends) has long been known as a contributor to the history of medieval chemistry-more particularly of that transitional Paracelsian epoch which was contemporary with various other great movements of exploration, renaissance and reform. It was only natural, therefore,

that Professor Stillman in his present "Story of Early Chemistry" should focus the reader's attention upon Paracelsus as the dominant figure in chemistry before the foundation of the modern science by Lavoisier. The historian's estimate of the relative importance of personages or events is indicated by the amount of space which he gives to their consideration and if this be our standard the following series will indicate the comparative stress which Professor Stillman has placed upon the life and work of a few names in early chemistry-Boerhaave (2 pages), Glauber (4), Helmont (5), Zosimus (7), Cavendish (7), Scheele (8), Albertus Magnus (9), Agricola (10), Boyle (12), Roger Bacon (15), Priestley (15), Paracelsus (19), Lavoisier (25). While there may well be an objection, from our present viewpoint, to the historian of chemistry giving as much attention to Zosimus as to Cavendish, or to Roger Bacon as to Priestley, it must be remembered, as Professor Stillman so clearly indicates, that personal influence can not always be measured by the number of original discoveries.

The history of chemistry may be presented from either the descriptive, biographical, philosophical or literary points of approach. The first of these treatments will describe the important discoveries of chemistry, the second will depict its leading personalities, the third will unfold the development of its basic principles, and the fourth will review its documentary sources of information. The first two of these methods will appeal to the young student, while the last two will attract only persons of mature mind. While sharing somewhat in all these choices of treatment it is principally to the fourth, or literary, type of history that the present "Story of Early Chemistry" belongs. Professor Stillman, following the lead of Kopp, Lippmann, Sudhoff, Berthelot and other foreign investigators, makes a very critical examination of the original records. The authenticity of the chemical texts ascribed to Democritus, Aristotle, Geber, Avicenna, Lully, Basil Valentine, Paracelsus and other early writers is considered more exhaustively by him than by any other writer in English. Without showing the polemical and nationalistic temper of certain European historical scholars he has given a well-balanced estimate of the various conflicting opinions.

In a volume which deals so largely with questions of authorship, much of the material that would be considered by historians of other schools must necessarily be omitted. We may pardon, therefore, in Professor Stillman's volume the omission of any reference to the Pneumatika of the Greek mechanician Hero (the precursor of the pneumatic philosophers named in Chapter xii) or to the discovery of the prin

ciple of specific gravity by the Greek geometer Archimedes the most important contribution to the methods for studying the properties of matter that was made in ancient times. In the apparatus described by Hero and in the method of research devised by Archimedes the alchemists unknowingly possessed an infallible means for determining the character of their fictitious gold, and had they only applied this knowledge the world might have been spared that colossal waste of effort which played so long and so large a part in the story of early chemistry.

Professor Stillman passed away before the first proofs of his book were received from the publisher. This was doubly unfortunate, for had his life been spared a few months longer he might have been able before the final printing to round out his rather incomplete treatment of Arabian chemistry by citations from the important recently published "Arabische Alchemisten" by Julius Ruska. He would also have been enabled to devote that attention to proofreading and indexing which an author of Professor Stillman's meticulous care could only give. The book in consequence contains a considerable number of typographical errors, such as pennance (107), Euripedes (131), notorius (355), and many others. The nouns of German book titles are not capitalized and the endings os and us are used indiscriminately for Greek proper names. In the bibliography the Papyrus Graecus Holmiensis is incorrectly listed as a work of Bernard Palissy. Certain slips of composition would also undoubtedly have been detected by Professor Stillman in the proofreading, such as the statement (p. 136) that the name Chemeia was probably "derived from the Greek word chemi signifying black," where Egyptian was no doubt intended. Such errors as these, however, are of minor significance in comparison with the general excellence of the volume as a whole.

"The Story of Early Chemistry" is told by Professor Stillman in a particularly pleasing and interesting way. He unfolds before his readers a great drama of ideas in which the successive followers of Hermes, Paracelsus and Stahl are shown hopelessly groping for centuries in the dark until a final burst of light is shed upon the scene by the efforts of Lavoisier.

The many friends of Professor Stillman will appreciate the brief biographical sketch which has been added to the volume as a foreword by Professor S. W. Young, who gives a most delightful picture of the personality and many-sided activities of his departed colleague.

BUREAU OF CHEMISTRY, WASHINGTON, D. C.

C. A. BROWNE

SPECIAL ARTICLES

A NUTRITIONAL STUDY UPON A FUNGUS ENZYME1

POSSIBILITIES in a comparatively uninvestigated field of nutrition have been suggested by the feeding of a vegetable fungus enzymic material called protozyme to growing chicks in a preliminary test at the New Jersey Agricultural Experiment Station. Over a thousand Leghorn chicks of both sexes were used in the investigation for a period of seven weeks, after which the males were eliminated. The test has now continued for a period of twenty weeks. The birds in question are divided into five groups. All receive a normal scratch mixture daily of cracked cereal grains and a ground mash mixture of bran, middlings and corn meal. All have free access to liquid skim milk. The enzymic material is incorporated in the mash mixture as follows: 5 per cent. of the weight of the mash in Group 1, 3 per cent. in Group 2, 2 per cent. in Group 3, 1 per cent. in Group 4 and none in Group 5. Group 5, consuming no accessory enzymic material, acts as a check upon the other four groups. During the twenty-weeks' feeding in every instance the chicks consuming the enzymic material have manifested a more rapid growth than those not consuming it. The following table indicates the feed consumed and growth attained.

GASTRIC TRANSPLANTATION

THE study of gastric motility as ordinarily carried out is attended with many technical difficulties. It was conceived that it might be possible materially to reduce these difficulties by transplanting the stomach to a subcutaneous locus so that it could be viewed directly from the outside. Whether the animal could survive such an operation, maintain normal nutrition and gastric movements was the crux of the problem. The problem was attacked in the following way, using young albino rats. The animals were given no food for twenty-four hours before the operation and none for twenty-four hours after. A median longitudinal incision of 2 cm was made through the abdominal wall along the linea alba. The stomach was lifted through this opening and the abdominal muscles sutured together beneath it, but leaving openings. sufficient to transmit the esophagus and the pylorus. These structures were anchored to the abdominal wall by two stay sutures each. Then the integument was dissected back from the muscle laterally on each side to form a pouch for the stomach. The cut edges. of the skin were brought together and held by continuous sutures closing the incision. Thus the stomach was covered on the outside by skin and lay between the skin and the abdominal muscles. In two weeks the incision was healed and the animal ready to be observed. Of ten animals first subjected to the operation five lived. Later five more animals were operated on and all lived for considerable periods. Three are alive and apparently normal at the end of nine months. These have been studied with care. They show a normal weight graph, normal appetite and apparently normal peristalsis. They have at no time shown signs of esophageal or pyloric stasis.

The contour of the stomach and its contraction waves can readily be seen through the skin. To permit study of these contractions the rat is placed in a small glass-bottomed cage. This cage is suspended above a bench upon which the observer reclines.

At present the writer is working on the question of the relation between gastric contractions and muscular activity. The observation cage is suspended from one end of a Fitz pneumograph (Porter type) which is connected through rubber tubing with a tambour (Durrant method).1 This is a highly sensitive method of detecting movements of the animal. For example, the rat's nibbling a grain of corn sets the system into marked oscillations. The tambour is adjusted to write on a revolving extension kymograph drum. Below the tambour lever is adjusted a signal magnet with simple key in circuit and a chronograph. 1 Durrant, Am. J. Physiol. (Balt.), 1924, 70, 344.

A point is marked on the skin about half way between the cardiac and pyloric ends of the stomach. Whenever a wave is seen passing this point the simple key is closed, thus recording it on the drum. A single stroke represents a shallow wave, two strokes a medium and three strokes a deep wave. When the animal shifts its position so as to obscure the view the signal key is depressed until a readjustment of the posture is secured.

A fairly high correlation between muscular movements and gastric peristalsis as postulated by Richter2 is evident. Frequently in the quiescent animal gastric contractions become shallow or apparently entirely cease. These suddenly become deeper, whereupon the animal at once arouses to activity and carries out sundry movements, such as washing or scratching. More frequently, however, it has been observed that muscular activity immediately precedes rather than follows augmented gastric motility.

A detailed account of the observation will be published later.

DEPARTMENT OF PHYSIOLOGY OHIO STATE UNIVERSITY

MYRON H. POWELSON

THE IOWA ACADEMY OF SCIENCE THE thirty-ninth annual meeting of the Iowa Academy of Science was held at the Iowa State Teachers College, Cedar Falls, Iowa, on May 1 and 2, 1925.

Officers were elected as follows: President, R. I. Cratty, State College; vice-president, C. E. Seashore, State University; secretary, P. S. Helmick, Drake University; treasurer, A. O. Thomas, State University; editor, Willis DeRyke, State University; representative to American Association for the Advancement of Science, D. W. Morehouse, Drake University. The following papers were presented:

BACTERIOLOGY

(Iowa State College Branch, Society of American Bacteriologists.)

Section Chairman, Max Levine, State College, Ames. Some notes on trickling filters in the purification of creamery wastes: MAX LEVINE.

Bacterial decomposition of sugars and acids: JOHN H. WATKINS.

Yeasts in bottled carbonated beverages: W. R. TURNER. Effect of reaction on the growth of yeasts: J. C. WELDIN.

The development of metallic flavor in buttermilk: M. P. BAKER and B. W. HAMMER.

The influence of carbon dioxide on the quality and keeping qualities of butter and ice cream: F. F. SHERWOOD.

2 Richter, Comp. Psychol. Monogr., 1922, 1, Serial No. 2, September.

Section Chairman, G. W. Martin, State University, Iowa City.

Genetic correlation between fruit size and color in the tomato: E. W. LINSTROM.

Some Aminitas from eastern Iowa: G. W. MARTIN. Notes on Iowa fungi—1924: G. W. MARTIN. Some soil and moisture relationships of sweet gum and river birch in southern Maryland: FRED B. TRENK.

The occurrence of hickories in Iowa in relation to soil types: FRED B. TRENK.

The formation of root hairs in water: CLIFFORD H. FARR.

Ceratophyllum demersum in West Okoboji lake: EDWARD N. JONES.

Microsporogenesis in Cucurbita maxima: EDWARD F.

CASTETTER.

Chromosome studies of Zea Mays L.: R. G. REEVES. An abortive lily anther: CHARLES A. HOFFMAN. Some wound responses of citrus leaves: ROBERT B. WYLIE.

Culture studies on Psilocybe coprophila: KATHRYN GILMORE.

A partial list of the parasitic Ascomycetes of Iowa: JOSEPH C. GILMAN.

A trip in the Iron Range Country: L. H. PAMMEL. Some notes on the flora of Forest and Florence counties, Wisconsin, and Iron county, Michigan: L. H. PAMMEL.

Germination of some pines and other trees: L. H. PAMMEL and C. M. KING.

Our native plants (an article appearing in the Iowa Farmer and Horticulturist, Vol. 1, No. 7, Nov., 1853): L. H. PAMMEL.

A provisional list of the species of Septoria in Iowa: B. N. UPPAL.

A tree census of Mount Pleasant, Iowa: H. E. JAQUES. The physiographic ecology of a Wisconsin drift lake: LOIS A. CATLIN and ADA HAYDEN.

Iowa in the botanical manuals: B. SHIMEK. Deforestation and stream pollution: B. SHIMEK. Some noteworthy Iowa fungi of 1925: GUY WEST WILSON.

CHEMISTRY

(Iowa and Ames Sections, American Chemical Society.)