We have obtained similar results as to oxygenated water.1 Certain investigators have thought that this was produced and caused the sterilization and would itself render the water dangerous for alimentary use. Such an explanation is false and the fear groundless. But a trace of oxygenated water was formed after several hours' exposure to the rays. There was never any oxygenated water formed during the short passage of the water about the lamp necessary for the sterilization.

CHEMICAL MODIFICATION OF THE WATER TREATED WITH THE ULTRAVIOLET RADIATION.

Chemically water is very little altered by the ultra-violet rays, certainly during the short time required for the sterilization.

With Th. Nogier and Rochaix,' I have shown that an exposure of 10 minutes (lamp immersed in a basin of water only a few centimeters deep) hardly altered the chemical composition of the water. The organic matter, ammonia, the nitrites, the nitrates, and other substances dissolved, were almost always in the same proportions at the end of 10 minutes; they were not in the least transformed by the passage (several seconds) in an immersion apparatus, a length of passage sufficient for complete sterilization.

We add that the taste and odor of the water are not altered.

THE WATER THUS TREATED IS HARMLESS.

Although the chemical composition of the water is not changed by the ultra-violet rays, the question as to its harmlessness yet remains. Is the water thus sterilized harmless?

We have fed daily for a month dogs, rabbits, and guinea pigs with water from a Nogier apparatus. Nothing in their general health, in their weight, or their temperature indicated the least ill effect.

THE ACTION OF THE ULTRA-VIOLET RADIATION ON THE FLUORESCENT MATTER CONTAINED IN WATER.

3

Concerning the processes for controlling the sterilization of water, Dienert has made a very interesting note. There exist in all surface waters fluorescent matter of organic origin. Sterilization by the ultra-violet rays (as well as by ozone or otherwise) causes a notable decrease in the quantity of such matter. Water treated by these rays

differs therefore in this respect from the natural river water before its passage through our apparatus.

1 J. Courmont, Th. Nogier et Rochaix. C. R. Ac. des Sciences, 30 mai 1910.

2 J. Courmont, Th. Nogier et Rochaix. C. R. Ac. des Sciences, 12 juillet 1909.

3 Dienert. C. R. Ac. des Sciences, 21 février 1909.

ACTION OF THE ULTRA-VIOLET RADIATION UPON TOXINES.

It may be asked whether the poisons resulting from the microbes and which may be contained in the water (in small quantities, of course) are destroyed by the ultra-violet rays. We are in a position to answer this question.

The toxines such as we have been able to obtain in our bacteriological laboratories can not be destroyed by the ultra-violet rays since they form a liquid very rich in colloidal matter and therefore not transparent to this radiation. It would therefore be necessary to work with very thin strata of the liquid. We have demonstrated this with the tetanus toxine.1 A very long exposure (one hour under 1 to 2 cm.) scarcely weakened the toxic power of a fibrous culture of the Nicolaier bacilli. If the toxine is sufficiently diluted with water, say 1 part in 2,000, it is neutralized in a few minutes. Cernovodeanu and V. Henri have obtained similar results. 3

Toxines are, therefore, very sensitive to the action of the ultraviolet rays provided they are so diluted as not to be protected from them by their colloidal state. Such toxines as are apt to be found in potable water will, therefore, be destroyed as well as the microbes.

PRACTICAL APPLICATIONS.

Are the preceding results capable of practical application? Surely. They give rise to a simple and very powerful new method of sterilization, applicable wherever an electrical current (continuous or transformed) is at hand.

The water is not changed or warmed. Nor is it harmful for drinking.

The only condition necessary for the successful sterilization is the transparency of the water; filtration would, therefore, be necessary for muddy water.

Our apparatus can serve three purposes: First, household sterilization (special small-sized apparatus adapted to the supply pipe of an apartment). Second, sterilization for larger establishments (apparatus with greater flow of water placed at the entrance of the water into the building and furnishing sterile water to all the faucets of a hotel, barracks, hospital, school, etc.). Third, sterilization of water for a city (apparatus capable of purifying, if necessary, several thousand cubic meters of water per day; apparatus with which trials are actually being made).

For household apparatus, and even for such as is destined for larger establishments, it is desirable to have some automatic device to stop

the flow of water whenever the lamp may not work either through accident or design. Surveillance of the apparatus would then be unnecessary. Only sterile water could be drawn.

Such apparatus as we have described in this article would be of great advantage in certain professions and industries. Surgeons, obstetricians, could have sterile water; pharmacists would feel secure in the preparation of aseptic compounds; brewers would have great advantage in using sterile water. Water thus sterilized could be used by dairymen, beer makers, manufacturers of artificial mineral waters or bottlers of natural water (washing of bottles), etc.

The applications which Th. Nogier and I have made of the bactericidal power of the ultra-violet rays in the sterilization of water have, therefore, an important practical bearing which no one now contests.

THE LEGAL TIME IN VARIOUS COUNTRIES.1

[With colored map.]

By Dr. M. PHILIPPOT,

Astronomer at the Royal Observatory of Belgium.

TIME IN GENERAL.

Time is measured by the rotation of the earth about its axis. A day is defined as the time taken for one complete rotation. It is assumed that the axis is fixed in the earth and that the rotation is uniform. In order to measure the time taken for this rotation, it is necessary to have reference marks both in the sky and on the earth. For the latter the meridian is chosen, which is the plane passing through the earth's axis and vertical to the place where the time is measured. Two points are used in the sky: The first, the vernal equinox, which is the ascending node (intersection) of the ecliptic upon the equator; the second is the sun's center."

The vernal equinox serves to determine the sidereal day, which is the time between two successive passages of the equinoctial point over the upper meridian of a place. The moment of this passage is taken as the beginning of the sidereal day. The hour angle of the vernal equinox gives the local sidereal time. For the affairs of civil life sidereal time is inconvenient and not used. It is used only for astronomical purposes.

The center of the solar disk is used to define the true solar day. On account of the variable movement of the sun along the ecliptic, the length of the true solar day varies from day to day and it is not feasible to make mechanisms or clocks keeping time with these irregularities. A fictitious sun has therefore been imagined, running its course along the ecliptic at a regular rate and reaching the points of its orbit nearest to and farthest from the earth at the same times as the true sun. A second imaginary sun is likewise supposed to pass along the celestial equator at a uniform rate and to be at the vernal equinox at the same moment with the first fictitious sun. This second imaginary sun is called the mean sun. The day measured by it

1 Translated by permission, with revisions by the author, from Annuaire Astronomique pour 1912 Belgium.

a The ecliptic is the intersection with the celestial sphere of the plane passing through the earth's orbit. The equator is the intersection with the celestial sphere of the plane passing through the earth's equator.