3. Experiments affording evidence for or against Each memoir must be accompanied by a sealed envelope enclosing the author's name and super- scribed by a motto corresponding to one borne by the manuscript, and must be handed to the Secre- tary on or before April 1, 1894. NEW METHOD OF PROTECTING BUILDINGS FROM LIGHTNING. SPARE THE ROD AND SPOIL THE HOUSE! Lightning Destroys. Shall it be Your House or a Pound of Copper? IN seeking a means of protection from lightning-discharges, we have in view two objects, the one the prevention of damage to buildings, and the other the prevention of injury to life. In order to destroy a building in whole or in part, it is necessary that work should be done; that is, as physicists express it, energy is required. Just before the lightning-discharge takes place, the energy capable of doing the damage which we seek to prevent exists in the column of air extending from the cloud to the earth in some form that makes It capable of appearing as what we call electricity. We will therefore call it electrical energy. What this electrical energy is, it is not necessary for us to consider in this place; but that it exists there can be no doubt, as it manifests itself in the destruction of bulldings. The problem that we have to deal with, therefore, is the conversion of this energy into some other form, and the ac- complishment of this in such a way as shall result in the least injury to prop- When lightning-rods were first proposed, the science of energetics was en- tirely undeveloped; that is to say, in the middle of the last century scientific men had not come to recognize the fact that the different forms of energy- heat, electricity, mechanical power, etc.- were convertible one into the other, and that each could produce just so much of each of the other forms, and no more. The doctrine of the conservation and correlation of energy was first clearly worked out in the early part of this century. There were, however, some facts known in regard to electricity a hundred and forty years ago; and among these were the attracting power of points for an electric spark, and the conducting power of metals. Lightning-rods were therefore introduced with the idea that the electricity existing in the lightning-discharge could be con- veyed around the building which it was proposed to protect, and that the The question as to dissipation of the energy involved was entirely ignored, naturally; and from that time to this, in spite of the best endeavors of those interested, lightning-rods constructed in accordance with Franklin's principle have not furnished satisfactory protection. The reason for this is apparent when it is considered that the electrical energy existing in the atmosphere before the discharge, or, more exactly, in the column of dielectric from the cloud to the earth, above referred to, reaches its maximum value on the sur- face of the conductors that chance to be within the column of dielectric; so that the greatest display of energy will be on the surface of the very lightning- rods that were meant to protect, and damage results, as so often proves to be It will be understood, of course, that this display of energy on the surface of the old lightning-rods is aided by their being more or less insulated from the earth, but in any event the very existence of such a mass of metal as an old lightning-rod can only tend to produce a disastrous dissipation of electrical energy upon its surface,-"to draw the lightning," as it is so commonly put. Is there a Better Means of Protection? Having cleared our minds, therefore, of any idea of conducting electricity, and keeping clearly in view the fact that in providing protection against light- ning we must furnish some means by which the electrical energy may be harmlessly dissipated, the question arises, "Can an improved form be given Terre Haute, Ind. A College of Engineering. Well endowed, well equipped. Courses in Me- chanical, Electrical, Civil Engineering, and Chem- istry. Extensive Machine Shops. Laboratories, A Work of 204 pages, with 3 plates of 12 figures. Contains full descriptions of nearly one hundred species of Batrachians and Reptiles, together with abundant notes on their habits. The identification of the species made easy by means of analytical The Ornamental Penman's Pocketbook of Alpha- bets, for sign-writers, engravers, stone-cutters and Howard Cromwell, 50 cts. Practical Electrics: A A System of Easy Lettering, by Universal Handybook on Every-day Electrical Mat- ters, 135 pp., fully illustrated, 12mo, cloth. 75 cts. Notes on Design of Small Dynamo, by G. Halliday, 79 pp., with a number of plates to scale, 12mo, cloth, $1. The Phonograph and How to Construct It, by W. Gillett, 87 pp., 12 folding plates, 12mo, cloth, $2. SPON & CHAMBERLAIN, Publishers, 12 Cortlandt As the electrical energy involved manifests itself on the surface of conduc- tors, the improved rod should be metallic; but, instead of making a large rod, suppose that we make it comparatively small in size, so that the total amount of metal running from the top of the house to some point a little below the foundations shall not exceed one pound. Suppose, again, that we introduce numerous Insulating Joints in this rod. We shall then have a rod that experi- ence shows will be readily destroyed-will be readily dissipated when a discharge takes place; and it will be evident, that, so far as the electrical en- ergy is consumed in doing this, there will be the less to do other damage. The only point that remains to be proved as to the utility of such a rod is to show that the dissipation of such a conductor does not tend to injure other bodies in its immediate vicinity. On this point I can only say that I have found no case where such a conductor (for instance, a bell wire) has been dis- sipated, even if resting against a plastered wall, where there has been any material damage done to surrounding objects. Of course, it is readily understood that such an explosion cannot take place in a confined space without the rupture of the walls (the wire cannot be boarded over); but in every case that I have found recorded this dissipation takes place just as gunpowder burns when spread on a board. The objects against which the conductor rests may be stained, but they are not shattered, I would therefore make clear this distinction between the action of electri- cal energy when dissipated on the surface of a large conductor and when dis- sipated on the surface of a comparatively small or easily dissipated conductor. When dissipated on the surface of a large conductor, a conductor so strong as to resist the explosive effect, - damage results to objects around. When dissipated on the surface of a small conductor, the conductor goes, but the A Typical Case of the Action of a Small Conductor. Franklin, in a letter to Collinson read before the London Royal Society, Dec. 18, 1755 describing the partial destruction by lightning of a church-tower at Newbury, Mass, wrote, “Near the bell was fixed an iron hammer to strike the hours; and from the tail of the hammer a wire went down through a small gimlet-hole in the floor that the bell stood upon, and through a second floor in like manner; then horizontally under and near the plastered ceiling of that second floor, till it came near a plastered wall; then down by the side of that wall to a clock, which stood about twenty feet below the bell. The wire was not bigger than a common knitting needle. The spire was split all to pieces by the lightning, and the parts flung in all directions over the square in which the church stood, so that nothing remained above the bell. The lightring passed between the hammer and the clock in the above-mentioned w're without hurting either of the floors, or having any effect upon them (except making the gimlet-holes, through which the wire passed, a littl bigger), and without hurting the plastered wall, or any part of the building, so far as the aforesaid wire and the pendulum-wire of the clock extended; which latter wire was about the thickness of a goose-quill. From the end of the pendu- lum, down quite to the ground, the building was exceedingly rent and dam- aged.... No part of the aforementioned long, small wire, between the clock and the hammer, could be found, except about two luches that hung to the tall of the hammer, and about as much that was fastened to the clock; the rest being exploded, and its particles dissipated in smoke and air, as gun- powder is by common fire, and had only left a black smutty track on the plas- tering, three or four inches broad, darkest in the middle, and fainter towards the edges, all along the ceiling, under which it passed, and down the wall." One hundred feet of the Hodges Patent Lightning Dispeller (made under patents of N. D. C. Hodges, Editor of Science) will be mailed, postpaid, to any address, on receipt of five dollars ($5). Correspondence solicited. Agents wanted. Probably you take THE Electrical Engineer. JUST PUBLISHED. Imp. 8vo, Cloth, 430 pp. By Kegan Paul, Trench, Trübner & Co., London. Price, 31s. 6d. (less discount.) RACES AND PEOPLES. By DANIEL G. BRINTON, M.D. "The book is good, thoroughly good, and will long remain the best accessible elementary ethnography Most people interested in Electricity Comparative Philology of the Old and New in our language."—The Christian Union. do. If you do not, now is a good time to begin. It is published every Wednesday. Subscription, $3.00 per year. Worlds in its Relation to Archaic With an introduction on Race and Language, giving a résumé of the opinions of many of the principal writers on those subjects, accompanied by copious vocabularies and numerous tables of comparison for similar words and their cognate forms as for most of the chief families of languages, both ancient We "We strongly recommend Dr. Brinton's Races and Peoples' to both beginners and scholars. are not aware of any other recent work on the science of which it treats in the English language." -Asiatic Quarterly. "His book is an excellent one, and we can heartily recommend it as an introductory manual of ethnology.”—The Monist. "A useful and really interesting work, which deserves to be widely read and studied both in Europe You can try it three months for fifty and modern, conveniently arranged for purposes of and America.”—Brighton (Eng.) Herald. comparison. An immense number of words are given, and especially for Turanian (including Chinese, Accadian and Egyptian), as well as for African and American ones. The general results tend to show that there still exists in most languages, whether dead or living, New York, N. Y. a certain element of what may be called an Archaic The Electrical Engineer, 203 Broadway, Every reader of "Science" should subscribe for the AMERICAN ARCHITECT, THE OLDEST AND BEST Architectural publication in the country. Interesting articles on architecture. Sanitation, Archæology, Decoration, etc., by the ablest writers. Richly illustrated Issued weekly. Send stamp for specimen copy to the publishers, Residuum, more or less common to all. THE AMERICAN RACE. By DANIEL G. BRINTON, M.D. "The book is one of unusual interest and value."— Inter Ocean. "Dr. Daniel G. Brinton writes as the acknowledged authority of the subject.”—Philadelphia Press. "The work will be of genuine value to all who wish to know the substance of what has been found out about the indigenous Americans."-Nature. "A masterly discussion, and an example of the -Philadelphia Ledger. "This volume is most stimulating. It is written with great clearness, so that anybody can understand, and while in some ways, perforce, superficial, grasps very well the complete field of humanity."The New York Times. "Dr. Brinton invests his scientific illustrations and measurements with an indescribable charm of narration, so that 'Races and Peoples,' avowedly a record of discovered facts, is in reality a strong stimulant to the imagination."-Philadelphia Public Ledger. "The work is indispensable to the student who requires an intelligent guide to a course of ethnographic reading."-Philadelphia Times. Price, postpaid, $1.75. FOSSIL RESINS. This book is the result of an attempt to Ticknor & Co., 211 Tremont St., Boston. successful education of the powers of observation." collect the scattered notices of fossil resins, "Extremely useful to beginners and collectors for the region it covers."-Wm. H. Dall. MOLLUSKS OF THE Price, postpaid, $2. ATLANTIC COAST OF THE UNITED STATES. N. D. C. HODGES, 874 Broadway, N. Y POPULAR MANUAL OF VISIBLE SPEECH AND BRENTANO'S, Union Square, New York, VOCAL PHYSIOLOGY. For use in Colleges and Normal Schools. Price 50 cents Sent free by post by Chicago, Washington, London, Paris. GERMANIA A monthly magazine for the study of the German language and literaN. D C. HODGES, 874 Broadway, N. Y. ture, is highly recommended by college professors and the press as "the best effort yet made to assist Newspaper Clippings. 25,000 in Stock, the student of German, and to interest him in his pursuit." Its BEGINNERS' CORNER furnishes every What do you want? Let us know. We year a complete and interesting course in German can supply you. The Clemens News | grammar. $2 a year. Single copies 20 cents. P. O. Box 151, Manchester, N. H. Agency, Box 2329, San Francisco, Cal. The Boston Medical and MASSACHUSETTS. A FIRST-CLASS WEEKLY MEDICAL NEWSPAPER. ESTABLISHED 1828. Terms of Subscription: In the United States, and to Canada and Mexico, $5 00 a year in ad To Foreign Countries embraced in the Universal Postal Union, $1.56 a year additional. Single numbers, 15c. Ten consecutive numbers free by mail on receipt of $1.00. vance. This JOURNAL circulates chiefly through the New England States, and is seen by the great majority of the profession in that important district. As a means of reaching physicians it is unequalled. It is under the editorial management of Dr. George B. Shattuck, assisted by a large staff of competent coadjutors. Subscriptions and advertisements received by the undersigned, to whom remittances by mail should be sent by money-order, draft or registered letter. DAMRELL & UPHAM, 283 Washington Street, Boston, Mass. exclusive of those on amber. The work is of interest also on account of descriptions given of the insects found embedded in these longpreserved exudations from early vegetation. By CLARENCE LOWN and HENRY BOOTH. 12°. $1. THE RADIOMETER. By DANIEL S. TROY. This contains a discussion of the reasons for their action and of the phenomena presented in Crookes' tubes. Price, postpaid, 50 cents. NEW YORK, JULY 7, 1893. HYDRAZOIC ACID: A NEW FORM OF APPARATUS FOR MOST of the text-books on the subject of chemistry in use at the present time still recognize but one compound of hydrogen and nitrogen, viz., ammonia. There are, however, now known to science, several compounds of these two elements. Of these the most important are ammonia, NH ̧; hydrazoic acid, HN,; and hydrazine, N,H4. There is a remarkable difference in the properties of the first two substances. Ammonia, the volatile alkali, has very strong basic properties, uniting directly with acids to form the ammonium salts. Only with the strongest basic elements does it act like an acid, forming sodium amide, NaNH2, with sodium, and potassium amide, KNH,, with potassium. Hydrazoic acid, on the contrary, is a comparatively strong acid. Being a binary compound of hydrogen and nitrogen, it might well be called hydronitric acid, after the analogy of hydrochloric acid, hydrobromic acid, etc. Its structural formula is represented thus: Thus we have at least six compounds of the elements hydrogen and nitrogen, their general formulas being : NH,, NH, NH, NH, NHa, and HN,. Heretofore hydrazoic acid and its derivatives have been made only by reactions1 of organic chemistry; but within the past few months a method has been devised by Wislecenus' by which the acid is made entirely from inorganic substances. This is done by first treating molten metallic sodium (or potassium) with dry ammonia gas, and then treating the sodium amide thus formed 1 Berichte der deutsch. Chem. Gesellschaft (Curtius), xxiii., 3023; xxlv., 3345. Ibid (Noeting and Grandmongin), xxiv., 2546. 2 Ibid, xxv., 2084. with dry nitrous oxide. The sodium salt of hydrazoic acid is thus formed; and, by treating this with dilute sulphuric acid, the hydrazoic acid itself is liberated, and may then be distilled off with water, thus giving a dilute aqueous solution. Wislecenus performed the operation in a small porcelain boat within a glass tube. The porcelain is strongly attacked by the sodium compounds, and the yield of hydrazoic acid which Wislecenus obtained was nearly 50 per cent of the theoretical amount, and, besides, only a small quantity of the acid (about one-half a gramme) could be made at a time. These objections to the apparatus used by Wislecenus induced the author to seek for a better form of apparatus with which to prepare the acid. A cylindrical copper air-bath was selected, which was provided with two mica windows placed opposite each other, through which any operation that was carried on within the bath could be easily observed. The bath was about fifteen centimetres from top to bottom and of about an equal diameter. The cover was of heavy asbestos board. In the centre of this a large circular opening was made, through which a glass beaker of 750 cubic centimetres capacity was inserted into the bath until its rim rested upon the asbestos board, the bottom of the beaker not being allowed to touch the bottom of the bath. A small quantity of clean sand was placed in the bottom of the beaker, and upon this a small iron sand-bath, hemispherical in shape, and having a capacity of 100 cubic centimetres. The mouth of the beaker was closed with a large flat cork, provided with three holes. Through the central hole passes a glass tube which reaches a little way into the iron dish, and through which the gases are conducted into the apparatus. The second hole carries a short exit tube, and the third a thermometer. Neither the metallic sodium nor the compounds formed have any action upon the iron dish, and the reactions which take place in the dish can be readily observed through the mica windows of the air-bath and the glass beaker. The ammonia gas was obtained by gently heating on a waterbath a flask containing strong ammonia water, and the nitrous oxide by the decomposition of ammonium nitrate by heat. The gases were dried as directed by Wislecenus, by passing them over soda-lime and solid potassium hydroxide. To perform the operation 25 grammes of metallic sodium were placed in the iron dish, the temperature of the bath raised to 300° - 360° C., and dry ammonia gas conducted in and delivered just above the surface of the molten sodium. The specific gravity of sodium being less than that of the amide formed, the metal floats on the surface until the action is finished. The reaction is represented by the equation: NH, + Na Na NH2 + H. = When the globules of sodium had all disappeared, the nitrous oxide was substituted for the ammonia, and the temperature of the bath lowered to 230° — 250° C. Two reactions now take place. The two atoms of hydrogen in the sodium amide are replaced by the bivalent group, Ng, contained in the nitrous oxide, the hydrogen and oxygen uniting to form water. This then reacts with a second molecule of sodium amide, forming sodium hydroxide and ammonia: NaNH, + N,O =(NaNN,=NaN,) + H,O, and NaNH, +H,O = NaOH + NHg. The sodium compounds have a strong tendency to creep over the edge of the iron dish as fast as they are formed; but they only fall upon the sand in the bottom of the beaker, from which they are readily dissolved out by water. When the odor of ammonia ceases to be given off, the reaction is complete. The apparatus was allowed to cool, the mixture of sodium hydroxide and the sodium salt of hydrazoic acid was dis |