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Mineral Springs of Alaska
March, I918.] U. S. BUREAU OF STANDARDS NOTES.
415
convenient for use in connection with the proposed record sheet. The record forms for calorimeter tests which are shown in the circular have been used for some time and found to be complete and con'¢enie.nt. It is hoped that these forms Will be adopted wherever possible, so th:at there: will be greater uniformity in operating methods and the reco.rds used. The Bureau is willing to loan the original plates for preparation of electrotypes for these blanks to any one desiring to print them.
Mineral Springs of Alaska. ANol~. (U. S. Geological Survey Press Bulletin, No. 349, December, I917.)--Hot springs are widely distributed in Alaska, many of them yielding water that is near the boiling-point and remaining unfrozen the year round. During the Russian occupation of the territory primitive 'bathing-houses were built at several hot springs, notably near Sitka, and the hygienic value of the springs was recognized. I n recent years more elaborate bathing establishments have been constructed at several accessible hot springs, but some that are more difficult of access are occasionally visited by prospectors. The demand for more accurate information about the qualities of the thermal w:aters led to an investigation whose results are set forth in a recent publication of the United States GeologicM Survey, Department of the Interior--" Mineral Springs of Alaska," by Gerald A. Waring (Water Supply Paper 418). To obtain material for this report Mr.. Waring spent the field season of 19,15 in Alaska. He examined 23 springs and obtained notes on 37 others whose existence was not before known to the Survey. Among the springs described by Mr. Waring are a number that yield carbonated water, and others whose water is strongly sulphuretted or salty. More hot springs have been found in southeastern Alaska than in the interior, perhaps because this part of the territory is best known, and relatively few have been found in northern Alaska. Nevertheless, the report describes hot springs at 21 places in the .Yukon Basin and at 5 in Seward Peninsula. The report is illustrated by sketch maps that show the location of many of the springs. The quality of the spring waters was determined by analyzing samples collected by Mr. Waring, and is discussed in connection with their manner of occurrence and source. The report contains also a brief chapter on the chemical character of some of the surface waters, 'by Richard B. Dole and Alfred A. Chambers, ,who have brought together all the available analyses. Most of the analyses represent samples collected by exploring parties in 1914 and 1915. The discussion of the quality of the waters of the Yukon is based on samples Collected daily at Anvik from August
416
C~:RgENr T o p i c s .
[J. F. I.
23, I9I 5, to April 19, 1916 , and from June 14 to August 16, 1916. Analyses of these samples will form part of a special report on the quality of the surface waters of Alaska. Copies of Water-Supply Paper 418 may be obtained without charge by applying to the Director, United States Geological Survey, Washington, D. C. A c c o m m o d a t i o n and C h r o m a t i s m of the Eye. ANo~T. (The Optical Journal and Review of Optometry, vol. 41, No. 2, p, 94, January 3, I 9 1 8 . ) - - T h e human eye, because of its power of accommodation, is a refractive system with a mobile focus. A lens has no mobility of focus at all. The eye that is completely presbyopic also has no mobility of focus, and when a lens is prescribed for the use of a person completely presbyopic, there can be no mobility of focus. Sometimes elderly persons demand glasses with which they can see equally well far and near. If they do not stilt have sufficient accommodation, this demand cannot be met. Those who take this stand will be more easily convinced that they are asking impossibilities when they are told that what they need is another pair of eyes ; that the ability to focus far and near is not a property of the lens, but of the human eye, which is lost in later life. When this power of the eye is lost, glasses cannot restore it; all the glasses can do is to make vision clear for just one point, far or near. Chromatic aberration is not noticeable in the eye under usual conditions, and yet the retinal image of any bright object is not a simple image. It is multiple in nature and made of several different colors. The reason we do not see the colors is because the eye is very sensitive to yellow rays and muc~h less so to all the others, the result being that we unconsciously disregard all but the image formed by the yellow rays. By looking at the small bright light through glass that only passes red and violet light, as for instance co.bait-blue glass, and at the same time wearing a correction that keeps the accommodation relaxed, we can measure the chromatism of the eye. Using the cobalt-blue glass in this way, and focussing for the violet, which puts the red out of focus, we compare the width of the red border to the light with the width of the light, and then make a calculation on the basis of the diameter of the pupil of the observing eye, the result of which will express in diopters the amount of chromatic aberration, which is usually found to be about 1.5o. While, as a rule, a person is not conscious of colored borders to bright objects, yet there are some exceptions where, for instance, the letters of test charts are seen bordered with colors. Usually in such cases the sight is slightly blurred, and removing the blur causes the colors to disappear. When this is not the case, there is no remedy for the condition; the subject must become accustomed to his chromatism and learn by practice to disregard it.
415
convenient for use in connection with the proposed record sheet. The record forms for calorimeter tests which are shown in the circular have been used for some time and found to be complete and con'¢enie.nt. It is hoped that these forms Will be adopted wherever possible, so th:at there: will be greater uniformity in operating methods and the reco.rds used. The Bureau is willing to loan the original plates for preparation of electrotypes for these blanks to any one desiring to print them.
Mineral Springs of Alaska. ANol~. (U. S. Geological Survey Press Bulletin, No. 349, December, I917.)--Hot springs are widely distributed in Alaska, many of them yielding water that is near the boiling-point and remaining unfrozen the year round. During the Russian occupation of the territory primitive 'bathing-houses were built at several hot springs, notably near Sitka, and the hygienic value of the springs was recognized. I n recent years more elaborate bathing establishments have been constructed at several accessible hot springs, but some that are more difficult of access are occasionally visited by prospectors. The demand for more accurate information about the qualities of the thermal w:aters led to an investigation whose results are set forth in a recent publication of the United States GeologicM Survey, Department of the Interior--" Mineral Springs of Alaska," by Gerald A. Waring (Water Supply Paper 418). To obtain material for this report Mr.. Waring spent the field season of 19,15 in Alaska. He examined 23 springs and obtained notes on 37 others whose existence was not before known to the Survey. Among the springs described by Mr. Waring are a number that yield carbonated water, and others whose water is strongly sulphuretted or salty. More hot springs have been found in southeastern Alaska than in the interior, perhaps because this part of the territory is best known, and relatively few have been found in northern Alaska. Nevertheless, the report describes hot springs at 21 places in the .Yukon Basin and at 5 in Seward Peninsula. The report is illustrated by sketch maps that show the location of many of the springs. The quality of the spring waters was determined by analyzing samples collected by Mr. Waring, and is discussed in connection with their manner of occurrence and source. The report contains also a brief chapter on the chemical character of some of the surface waters, 'by Richard B. Dole and Alfred A. Chambers, ,who have brought together all the available analyses. Most of the analyses represent samples collected by exploring parties in 1914 and 1915. The discussion of the quality of the waters of the Yukon is based on samples Collected daily at Anvik from August
416
C~:RgENr T o p i c s .
[J. F. I.
23, I9I 5, to April 19, 1916 , and from June 14 to August 16, 1916. Analyses of these samples will form part of a special report on the quality of the surface waters of Alaska. Copies of Water-Supply Paper 418 may be obtained without charge by applying to the Director, United States Geological Survey, Washington, D. C. A c c o m m o d a t i o n and C h r o m a t i s m of the Eye. ANo~T. (The Optical Journal and Review of Optometry, vol. 41, No. 2, p, 94, January 3, I 9 1 8 . ) - - T h e human eye, because of its power of accommodation, is a refractive system with a mobile focus. A lens has no mobility of focus at all. The eye that is completely presbyopic also has no mobility of focus, and when a lens is prescribed for the use of a person completely presbyopic, there can be no mobility of focus. Sometimes elderly persons demand glasses with which they can see equally well far and near. If they do not stilt have sufficient accommodation, this demand cannot be met. Those who take this stand will be more easily convinced that they are asking impossibilities when they are told that what they need is another pair of eyes ; that the ability to focus far and near is not a property of the lens, but of the human eye, which is lost in later life. When this power of the eye is lost, glasses cannot restore it; all the glasses can do is to make vision clear for just one point, far or near. Chromatic aberration is not noticeable in the eye under usual conditions, and yet the retinal image of any bright object is not a simple image. It is multiple in nature and made of several different colors. The reason we do not see the colors is because the eye is very sensitive to yellow rays and muc~h less so to all the others, the result being that we unconsciously disregard all but the image formed by the yellow rays. By looking at the small bright light through glass that only passes red and violet light, as for instance co.bait-blue glass, and at the same time wearing a correction that keeps the accommodation relaxed, we can measure the chromatism of the eye. Using the cobalt-blue glass in this way, and focussing for the violet, which puts the red out of focus, we compare the width of the red border to the light with the width of the light, and then make a calculation on the basis of the diameter of the pupil of the observing eye, the result of which will express in diopters the amount of chromatic aberration, which is usually found to be about 1.5o. While, as a rule, a person is not conscious of colored borders to bright objects, yet there are some exceptions where, for instance, the letters of test charts are seen bordered with colors. Usually in such cases the sight is slightly blurred, and removing the blur causes the colors to disappear. When this is not the case, there is no remedy for the condition; the subject must become accustomed to his chromatism and learn by practice to disregard it.