June 12, 1896.] 



SCIENCE. 



867 



VARIATIONS OF GLACIEES. 



To THE Editok of SCIENCE : At the Inter- 

 national Congress of Geologists at Zurich in 

 1894 a committee, with members representing 

 various countries, was appointed to collect and 

 make observations on the changes which are 

 continually occurring in the length and thick- 

 ness of glaciers. Much information bearing 

 on the variations of the Alpine glaciers has al- 

 ready been collected, and it is now desirable to 

 know something of the variations of glaciers in 

 other parts of the world, to determine whether 

 these variations are synchronous on different 

 continents and on opposite sides of the equator. 

 To what extent the variations of glaciers are 

 dependent on meteorological changes, and to 

 what extent on the size and shape of reservoirs, 

 etc. , is a problem whose solution is hoped for. 



Many of your readers will doubtless visit 

 American glaciers this summer, either on the 

 Pacific Coast, in Canada or in Alaska ; and I 

 hope they will take sufficient interest in the sub- 

 ject to make observations which will be of value. 



The information most desired regarding any 

 glacier is whether it is advancing or retreating. 

 In a memorandum issued by the Alpine Club 

 the following criteria are given : 



" When the ice is advancing the glaciers generally 

 have a more convex outline, * * * and piles of fresh 

 rubbish are found shot over the grass of the lower mo- 

 raines. Moraines which have been comparatively re- 

 cently deposited * * * are disturbed, show cracks, 

 and are obviously being pushed forward or aside by 

 the glacier. 



"When the ice is in retreat the marks of its fur- 

 ther recent extension are seen fringing the glacier 

 both at the end and sides * * * ; the glacier fails to 

 fill its former bed and hare stony tracts, often inter- 

 spersed with pools or lakelets, lie between the end of 

 the glacier and the mounds of recent terminal mo- 

 raines. ' ' 



For recording the extent of a glacier at the 

 time of one's visit, many methods have been 

 given. Among the simplest is to measure (or 

 pace) the distance from the end of the glacier 

 to some prominent rock, or to the line connect- 

 ing two easily recognizable points on opposite 

 sides of the valley. All photographs of the end 

 of a glacier are useful, especially those taken 

 from a station easily accessible and easily de- 



scribed ; photographs taken from the same 

 station at a future date will show what changes 

 have taken place in the interval. 



Excellent results can be obtained from the 

 following method : Select two stations on op- 

 posite sides of the valley a little below the 

 glacier's end ; mark and describe them ; esti- 

 mate their distance apart if no more accurate 

 determination can be made ; take a photograph 

 of the glacier's end from each of these stations, 

 and determine by compass the angle between 

 the ottier station and two or three prominent 

 peaks or other features that appear iu each 

 photograph. The photographs, the angles and 

 the distance between the stations will be suf- 

 ficient data to make a rough map of the 

 glacier's end.* All photographs and observa- 

 tions sent to me will be carefully preserved as a 

 part of a permanent record of American glaciers. 



Muir glacier, Alaska, is so frequently visited 

 that we should obtain a pretty complete history 

 of its changes. A photograph of the north- 

 western corner of the inlet, taken from the ship 

 when at anchor, or, better still, from the pro- 

 jecting bluff on the eastern side of the inlet, will 

 greatly help in making the record. 



The few observations which have already 

 reached me show that the glaciers about Glacier 

 Bay, Alaska, the Illecellewaet, in the Selkirks, 

 and those on Mt. Eainier, Washington, are re- 

 treating. Haeey Fielding Reid. 



Johns Hopkins University, 



Baltimoee, Md., May 23, 1896. 



LIFE habits of PHRYNOSOMA. 



Prof. Chas. L. Edwards's article on there- 

 production of Phrynosoma cornutuvi (Science, 

 May 22, 1896) interested me very much, in- 

 deed; but in some respects the article is mis- 

 leading, as one might suppose from reading it, 

 that Prof Edwards believes that all the species 

 of lizards of the genus Phrynosoma are oviparous, 

 as he found P. cornutum to be. This is, how- 

 ever, by no means the case, for, as I have pointed 

 out in Science over ten years ago (September 

 4, 1885, pp. 185-186), Phrynosoma douglassii is 

 strictly viviparous, and its period of gestation 



*A fuller account of the desired observations is 

 gbi en in the Journal of Geology, Chicago, Vol. III., 

 1895, pp. 284-288. 



