the latitude of the place of observation; corresponding simply with sidereal time at the Pole, and being infinite at the Equator. The pendulum had a period of eight seconds for each vibration. It continued in motion, with a single impulse, for six hours, making complete rotation in thirty-one hours, and a deviation of 1' 33" in each oscillation. By this noble experiment he substantiated an important physical fact, namely, the fixedness of the plane of oscillation as a consequence of vis inertia in matter generally. This he afterwards demonstrated still more ingeniously by means of a delicatelysuspended gyroscope. Another lessknown form of the experiment is also recorded in his works. A thin, long elastic rod of steel is fixed to the mandrel of an ordinary lathe, being free at the farther end. If this be pulled at the free end out of its position of rest, it vibrates in a series of lines, circles and ellipses, following each other in regular succession. The same phenomenon is seen in Wheatstone's kaleidophone. When, however, a steady oscillation has been obtained, it is not interfered with in direction by causing the mandrel and the attached rod to rotate rapidly about their axis; the plane of oscillation continuing stable, though the mass of the vibrating body is in motion. Even beyond this, the rotation protects the oscillatory plane against deformations due to unsymmetry of the rod, and renders it more stable than in a state of rest. Indeed, whatever form the vibratory curve may have taken up, whether linear, circular or elliptical, this is preserved unchanged as long as the axial rotation is kept at a certain speed.

At the meeting of the American Association for the Advancement of Science a very important contribution was read by Professor Graham

Bell, in which he described some discoveries made by himself and Mr. S. Tainter, which have resulted in the device of a new sound transmitter, comparable to the telephone, but the transmitting agent for which is light. The facts upon which this remarkable invention is based have been known for some time and have been referred to often in our Notes, but the conception of their application is wholly Professor Bell's. It will be anticipated, probably, by some readers that the now famous metal, selenium, forms a principal part in the invention, and was the chief subject of experiment in bringing the device into practical form. This metal, as was stated at some length in this Magazine recently, is intensely sensitive to light-vibrations. Molecular changes take place in it under the influence of light. But Professor Bell has been able to show by experiment that not only selenium, but also gold, silver, platinum, iron, steel, brass, copper, zinc, lead, antimony, German silver, ivory, celluloid, gutta-percha, paper, parchment, wood, mica and many alloys are all sensitive to light-vibrations. When the vibratory beam of light falls on these substances suitably prepared, they instantly send out sounds, the pitch of which depends on the frequency of the vibratory change in the light. Using selenium as an example, when the form or character of the lightvibration is controlled, the quality of the sound emitted is also controlled; and in this way articulate speech may be obtained. It thus appears that without a conducting wire, which is of course needful in all telephonic work dependent upon electric transmission, it is quite possible to speak -to cause audible articulate sounds -to be sent from station to station wherever it is possible to transmit a controlled beam of light. Thus it will be seen that the invention does not transmit sound-it simply pro

vides the means of causing certain predetermined sounds to be produced from a given station or point at a known and specified distance. The instrument has by no means been efficiently tested as to distance; but as a means of sound-transmitting through the agency of light, it has established itself. What its future applications may be, no one can clearly see it manifestly has many, and may become a powerful instrument in our civilized life. But a very curious application was suggested recently by Professor Bell himself. Visiting the solar observatory at Meudon, the Professor was very much impressed with M. Janssen's splendid solar photographs; and, after some reflection, expressed the opinion that the variations of brightness of a given solar point might make the Photophone speak, and so reproduce in the earthly laboratory the awful sounds poured forth by the fires on the sun! experiment has been actually tried; but hastily, and therefore without distinct success.

The

surface of the globe. On the books kept at the great Botanical schools and centres of cultivation, like Kew, there are just one hundred and thirty thousand species; thirty thousand of these belonging to countries in Europe and North America, where the flora are so admirably worked' that it would be difficult to find anywhere a new species, save at most a few cryptogams, and these scarcely so high in the scale as Ferns. The remaining one hundred thousand represent exotic plants more or less tropical and Southern; so that we may fairly double the number of these to allow for new species not discovered, giving thus two hundred thousand for these less-known regions, and making a total of two hundred and thirty thousand for the whole globe; excepting, however, countries not yet known to us botanically. Adding twenty thousand for these, we reach a minimum of two hundred and fifty thousand specific vegetable forms or plants on the whole surface of the globe.

Of varieties,' of course, there could be no computation.

M. Yung, of Geneva, recently read a paper to the Helvetic Society of Sciences on organic dust or germs in the atmosphere. It was of interest as being a contribution to a question which is of the highest importance to health and civilization. In the influence of this 'dust,' carried in the air, on public health the author distinguishes two groups of particles: the spores of fungi of the mould and mildew type-mostly microscopic; and the germs of the Micro-Bacteria. These latter are very properly held to be by far the more important. He agrees with M. Miquel's observations, to which we recently called attention, as made at Montsouris; for he observes a notable increase of germs during the hot months of summer, and a decrease

in winter. Having prepared flasks and filled them with a nutritive fluid which was perfectly sterilized, and the flask itself hermetically sealed, he took them and opened them to the access of air on mountains, glaciers and ocean, to the Mediterranean, in volcanic craters and in various other places and circumstances; and he has found that in most cases ten to twenty cubic centimetres of air sufficed to introduce germs of organisms capable of growing and living in successive or simultaneous generations according to 'species.' Two exceptions are noted; one being the flask opened at Geneva after an abundant fall of snow-the fluid remaining quite clear and uninfested, proving that a prolonged snowstorm is a means by which the air is cleansed of its germs. The other was an isolated ward of a Geneva Hospital.

On the other hand, fresh snow, gathered in winter on the mountains round Geneva, confirmed the former results as to the extreme diffusion of microscopic organisms. But the connection between the presence of endemics and epidemics, and the increased accession of germs, has not yet been sufficiently worked out.

But in the Bulletins of the Academy of Science at Munich there is the report of a discovery of extreme interest and importance, quite germane to this matter. Hans Buchner has succeeded in transforming a minute septic or putrefactive organism which is always associated with a certain disease, into another, extremely like it generally, but which has no connection with the disease. He reached his results by a continuous treatment of the forms in question for six months; and by producing fifteen hundred generations. In this way he was able to change the bacterium associated with the painful disease known as splenetic fever, into some of the forms of bacteria common to infusions of hay, and having no known

connection with specific disease. On the other hand, he changed the hayinfusion forms into spirillum volutans -the organism of splenetic fever: In the course of his experiments he came upon the intermediate forms between these; and affirms that the bacteria in the ordinary hay-infusion produces ten complete cyclic generations per day.

At a recent meeting of the French Academy, M. M. Hautefeuille and Chappuis announced that they had liquefied ozone. They have been able to ozonize oxygen to a greater extent than has hitherto been done, by passing a silent electric discharge through the oxygen at a low temperature. The tube containing the oxygen was immersed in liquid methylic chloride, which boils at -23°. After exposure to the electric discharge in this low temperature, the gas was conducted into the capillary tube of the Cailletet apparatus, and maintained at the same temperature.

After a few strokes of the pump of this beautiful machine, the gas in the tube appeared azure blue; as pressure increased, the colour deepened, until, under a pressure of several atmospheres, the ozonized oxygen appeared dark indigo in hue. The pressure was increased to ninety-five atmospheres and then suddenly removed, when liquefaction instantly ensued.

If the gas be rapidly compressed at ordinary temperatures, much heat is evolved and the gas explodes. It is much more easily liquefied than oxygen; in the ratio, in fact, of ninety to three hundred.

One has often wondered what becomes of wasted or used pins and needles. Not less curious is the query what becomes of wasted corks. In these days of projected competition between the electric light and coal-gas, there will, for many reasons,

be an effort to find some less costly method of producing gas-a carbureted hydrogen with a full white flame-that will be less expensive to produce than it now is. This will be, if accomplished, a gain to all, but especially as a means of keeping longer our seams of coal.

Many things have been experimented upon with this object in view. Wood residues of various kinds, skins of apples and grapes and other organic substances yield a gas quite luminous; but nothing hitherto tried has produced such excellent results as cork waste, and M. M. d'Alna and Martin now seriously propose its distillation in closed vessels. They obtained permission to try cork-gas at the National Theatre of the Opera in Paris. The first experiment was made on the 7th of November last. The cork used was chiefly old bottle-corks and useless fragments cast away in the manufacture of corks. This was all

heated in a retort and adapted to the gas apparatus of M. Schreiber, of St. Quentin. La Nature says that the gas burns with a most beautiful flame; it does not contain sulphides, and can be produced at an extremely low price. It is purified almost without apparatus, simply passing through a water purifier and a column of lime.

It will be known to our readers that besides the great scheme of M. Lesseps for cutting a canal across the Isthmus of Panama, by which a highway for ships may be made from sea to sea, an alternative scheme has been proposed by an American ; which is nothing less than a plan for conveying ships by rail-bodilyacross the Isthmus. For awhile this plan was ridiculed; but its

author has reduced it to a very commendable form, and it may yet be a formidable rival to the scheme of the great Frenchman.

The American engineer is named Eads. His project for the conveyance of ships by rail across the American Isthmus includes twelve rails placed four or five feet apart : the maximum pressure allowed to a wheel capable of sustaining twenty tons is five tons. The weight of the largest merchant ships fully laden is about six thousand tons; this weight would be distributed over one thousand two hundred wheels. Locomotives five times as powerful as the ordinary goods engines would be used, and arrangements would be made on either side of the Isthmus for the transfer of the ships from the sea to the rails, and from the rails to the sea. The average cost of all this is estimated at fifty millions of dollars. The cost of one canal such as M. Lesseps proposes would, it is declared, build a ship railway at four or five places along the Isthmus, equal in capacity to the canal, and several times more speedy in operation.

It is known that the flame of the safety-lamp used in mines elongates in air charged with fire-damp. M. Somzée proposes to utilize this property for the detection of this danger. A piece of metal is to be so placed in lamps variously fixed in the mine, that the presence of fire-damp elongating the flame shall cause the heating, and therefore expansion, of a piece of metal, which by expansion will make an electric contact and thus ring a warning bell. It has the advantage of simplicity, and the apparatus are at hand.

To the Rev. R. W. Allen.

Port Alfred,

DEAR SIR, April 14th, 1880. I joined the troops on Wednesday, April 16th, at the Lower Tugela, No. 1 Division, Major-General Crealock in command. In the camp we had the 99th Regiment, the 88th Connaught Rangers and the 3rd Buffs, Colonel Pearson (now General Pearson). We had also two batteries of Artillery, a large number of the Army Hospital Corps, the Army Service Corps and a company of Engineers. I saw many of the sick from all the regiments, as they were all brought to the base hospital at Fort Tenedos and Fort Pearson. When I first arrived in the camp, being somewhat deficient in my knowledge of military custom and rule, I had a little difficulty; but through the kindness of the Brigade-Major (Captain McGregor) and others, I got on nicely. The Corporal and the cook happened to be Wesleyans, which was an advantage to me. On the first night, I put down my blanket, and slept in the Corporal's tent; but next day I got a tent of my own, my own rations and a servant. My orders were signed by General Clifford, but not gazetted. I found this was not to my advantage, so I spoke to Major Walker (Adjutant-General), and on the 6th of May they were gazetted; and I was delighted to find that it gave such satisfaction to the officers in the camp, as they came to my tent to congratulate me. Being then in a better position, I was able to be freer in all my movements. I think Wesleyan Chaplains ought always to be put in the same position as representatives of other Churches. I believe I was able to do more good amongst the men by being put in orders.

The work amongst the men was commenced soon after my arrival, and I enjoyed it immensely up to the time of my removal. In my first visit to the hospital I found several Wesleyans, who seemed rather surprised, but greatly delighted, to see a Wesleyan Minister. I talked and prayed with all the men, not confining my attention entirely to the Wesleyans, but speaking to all who would listen; and I found them very wil. ling to listen, and glad to hear me read a chapter and pray with them. My plan was to get down by the stretchers and talk to all who were Protestants; and then, before leaving, read a chapter and pray. I did this in all the tents and marquees. I couldn't but enjoy it, as the men seemed so thankful for my visits. On Sunday, April 20th, we had

parade-service in the morning at 6.30, and I met Sergeant F and Sergeant Gboth apparently godly men. On the 22nd, I saw them carrying out a dead man, and it had such an effect on me that I decided, if possible, to visit all the men every day. There were soon so many that I couldn't do it; but I was there every day when in camp, and visited as many as possible. Once a week I visited the hospital at Stanger, which was a good distance from the camp.

For a little while I had to lie on the ground, but I soon got a stretcher from some of the men. On the Thursday I went into a tent and found a poor fellow very ill. I spoke to him, and he immediately burst into tears; he seemed surprised that I cared for a soldier. After a little while he got composed, and we had a talk. Next day, I went first to him, and was surprised to find him much better; the visit seemed to have done him good in his body as well as his soul. He continued to improve, and was eventually removed to Durban. About this time one of the surgeons was taken ill. I used to visit him every day. After some time he was removed to Stanger, where he died.

On Sunday, April 27th, we held paradeservice in the morning at nine; and in the afternoon held a meeting in the canteen. After this, I held service with a few men on the other side of the river. After a little while I got a lot of tracts and books sent me by Brother Nuttall, and I distributed them to the men, who read them eagerly. On April 30th, Craig came and told me of Lieutenant Thomson, (son of the Archbishop of York,) who was accustomed to attend his meetings. On May 1st, I again visited Stanger, and found one or two very interesting but severe cases. Next day, after riding back, I went into hospital, and found a man who had been flogged for drunkenness; he wanted to know what I thought of the justice of such proceedings. All I could tell him was that he should not have got drunk, and then he would not have been flogged. On May 2nd, at Stanger, I visited a Roman Catholic. I asked him if I should tell the Priest. He seemed very pleased when I returned. I told the Priest, and next day he went up to see him.

Next day, in visiting the hospital, I found five men in one tent all unconscious. I knelt down and prayed to God, and four of the five recovered. They all hau typhoid fever; one only was a Wesleyan. How sad I felt to see the poor fellows lying on