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SCIENCK 



[Vol. XVII. No. 423 



others, again, place a much higher and more extended 

 value upon their eflfectiveness as a means of development, 

 and, instead of employing their time to perfect their pupils 

 in' the knowledge and use of that language which alone can 

 introduce them to the world of thought and information, 

 exert themselves to extend their acquaintance with natural 

 and methodical signs, and to make them masters of panto- 

 mimic action. This to me is a most reprehensible practice 

 and a complete perversion of the true use of signs in the in- 

 struction of the deaf. 



Concerning the use of signs, Mr. Luzerne Rae says, "A 

 too abundant and constant use of signs is the grand practical 

 error of American institutions for the deaf and dumb." 



Dr. E. M. Gallaudet, president of the National Deat-Mute 

 College, in an able article in the American Annals, main- 

 tains that "until a deaf-mute can think freely in conven- 

 tional language, and express his thoughts fluently and cor- 

 rectly in the same, every instance of the use by him or to 

 him of the language of signs in its natural order, impedes 

 his progress toward the great end and object of his educa- 

 tion." 



In the oral instruction of the deaf, except in the earlier 

 stages, signs as a means of communication should be care- 

 fully prohibited ; in manual instruction they should be used 

 as sparingly as possible at all stages. If the deaf are to 

 satisfactorily acquire speech and speech-reading, they must 

 early learn to rely upon them for all purposes of communi- 

 cation ; and if they are to acquire fluency and correctness in 

 the written forms of tlie language, they must be required 

 constantly to express their ideas in the same. The continued 

 general use of signs will in either case prove highly detri- 

 mental to the great end and object of instruction, and no 

 intelligent teacher will prolong their exercise one moment 

 after they have served their legitimate purpose. Like the 

 scaffolding used in the erection of a building, which, how- 

 ever helpful and necessary during the course of construc- 

 tion, having served its purpose, is cast aside, with the com- 

 pletion of the edifice, as something not only unnecessary to 

 the strength and duration of the structure, but as something, 

 •which, if permitted to stand, would prove a most serious 

 debasement of its beauty and utility, so signs, however rapid 

 and convenient and helpful they may be as means of com- 

 munication and mental development, in the various stages 

 of intellectual growth, having served their purpose, should 

 be rigidly cast aside as debasing and detrimental to that 

 newer and more perfect language which it is their proper 

 function to aid in attaining. A. L. E. Ceoutee. 



TEMPERATURE IK THE GLACIAL EPOCH. ^ 



The late long frost has naturally suggested the question, "What 

 permanent fall of temperature would produce a recurrence of the 

 glacial epoch ? " It is a question not easily answered, for it is like 

 a problem complicated by too many independent variables. It is 

 not enough for us to ascertain the actual temperature of a district 

 in order to determine whether it will be permanently occupied by 

 •snow and ice. There are regions where the ground, a short dis- 

 tance below the surface, is always frozen to a depth of several 

 yards at least ; and yet glaciers do not occur, even among the 

 hills, because the amount of precipitation is so small that the 

 summer rapidly dissipates what the winter has collected. There 

 are other regions partly covered by ice, though their mean annual 

 temperature is distinctly above the freezing-point; as where gla- 

 ciers descend to the sea from hilly districts, of which a considera- 

 ble area lies above the snow-line, and on which there is much 

 precipitation. In the case of Great Britain, at least, a further 



' From Nature. 



difficulty enters into the problem ; namely, that much controversy 

 still prevails as to the interpretation of the symbols upon which 

 our inferences in regard to the temperature of these islands during 

 the glacial epoch must depend. Some authorities would concede 

 no more than that the highland districts of Scotland, Wales, and 

 England were enveloped in snow and ice, and the glaciers, 

 whether confluent or not, extended from their feet for a few leagues 

 over the lowlands, say. to some part of the coast of Lancashire 

 and of Northumberland ; while others desire to envelop a large 

 part of the British Isles in one vast winding-sheet of ice, a corner 

 of which even rested on the brow of Muswell Hill, above the val- 

 ley of the Thames. The one school regards the bowlder clay of 

 England as a deposit mainly submarine, the product of coast-ice 

 and floating ice in various forms : the other attributes it exclu- 

 sively, or almost exclusively, to the action of land-ice. Into this 

 thorny question we do not propose to enter. The approximation 

 which we shall attempt — and it can only be a rough one — can 

 be easily modified to suit the requirements of either party. 



We will assume throughout that the annual isothermal of 33° 

 coincides with the line of permanent snow. This, obviously, is an 

 assumption. Often, owing to small precipitation, it will be 

 found to be erroneous; but we take it as the only simple approxi- 

 mation, for, under favorable circumstances, masses of Ice may 

 protrude beyond it. 



The question, then, may be put in this form : ' ' Assuming a 

 sufiScient amount of precipitation, what changes of temperature 

 are required in order to bring within the isothermal of 33° regions 

 which are generally admitted to have been occupied by land-ice 

 during some part of the glacial epoch ? " 



First, in regard to the British Isles. All will admit that in 

 many places the Cumbrian and Cambrian glaciers descended to 

 the present sea-level. The mean temperature of the Thames 

 valley near London is 50° F. This isotherm outs the Welsh coast 

 a little east of Bangor. Obviously, the whole region north of this 

 line has a lower mean temperature ; no part of the British Isles, 

 however, being below 45". Hence a general fall of 18° would 

 give a temperature of 33°, at most, in the Thames valley and on 

 the shores of North Wales (except on the extreme west), while on 

 the coasts farther north the temperatures would range down to 

 37°. What would be the effect of this 'i Switzerland may enable 

 us to return an answer. The snow-line in the Bernese Oberland 

 may be placed roughly at 8,000 feet above the sea, but it is obvi- 

 ous that the chief feeding-ground of the Alpine glaciers lies rather 

 higher up in the mountains. In the case of such glaciers as the 

 Great Aletsch, or the Aar, the lowest gaps in their upper basins 

 are rather above 10,000 feet; while the surrounding peaks range, 

 roughly, from 13,000 to 14,000 feet, though but few exceed 13,000 

 feet. Thus the feeding-ground of the Oberland glaciers may be 

 regarded as equivalent to a mountain district the sky-line of which 

 ranges from rather above 3,000 to 5,000 feet. In reality, however, 

 not very much of it exceeds 4,000 feet above the snow-line. This, 

 indeed, rather overstates the case. We find practically that the 

 effective feeding-ground, that which gives birth to glaciers, which 

 protrude for some distance below their supply-basins, may be 

 placed about 1,000 feet above the ordinary snow-line; so that the 

 glacier-generating region of Switzerland may be regarded as 

 equivalent to a mountain district with passes about 1,500 feet, 

 and peaks not often exceeding 3,000 feet. It follows, then, that 

 if the temperature at the seacoast in North Wales were 33°, the 

 whole of the Scotch Highlands, and a large part of the Cumbrian 

 and Cambrian Hills, would become effective feeding-grounds, and 

 the glaciers would be able to descend into the plains. In the 

 Alps, the larger glaciers terminate at present at altitudes of from 

 4,000 to 5,500 feet (approximately); that is, they descend on an 

 average about 4,000 feet below the effective feeding-ground, or 

 3,000 feet below the snow-line. If the temperature of Bangor 

 were not higher than 33°, then the Snowdonian district would be 

 comparable with one of the Alpine regions where the mountains 

 rise generally from about 1,000 to 3,000 feet above the snow-line; 

 that is, with such a one as the head of the Maderanerthal, where 

 none of the peaks reach 13,000 feet above the sea. Here the Htifi 

 Glacier leads to passes rather below 10,000, among peaks of about 

 11,000 feet in altitude, and it terminates a little above 5,000 feet; 



