October 8, 1886.] 



SCIENCE. 



325 



miles about due south from the western arm of that 

 lake. To state the case is to prove its absurdity. So 

 much for Mr. Pearce Giles's latest version of ' Lake 

 Glazier.' Henry D. Harrowbr. 



753 Broadway, New York. 



Glaciers and glacialists. 



Mr. James D. Dana, in Science for Aug. 20, says, 

 " the memoirs of the Museum of comparative zoology, 

 founded by Mr. Alexander Agassiz, and not by his 

 father." In 1863, Prof. Louis Agassiz got a first 

 grant of ten thousand dollars from the legislature of 

 Massachusetts for the publication of those memoirs. 

 The first paper is by Theodore Lyman, and was issued 

 in March, 1865. The title is " Memoirs of the Museum 

 of comparative zoology, at Harvard college," vol. i., 

 Cambridge, 1864-65, 4" ; contents, illustrated cata- 

 logue, etc. More than twelve volumes have been 

 issued, the first three during Louis Agassiz's life. 



As to the accusation of ' Mr. Marcou's charge 

 against Mr. Alexander Agassiz,' etc., it is almost 

 superfluous — at least for those who have read my 

 paper — to say that I have made no charge of any 

 sort against Mr. Alexander Agassiz, and that his 

 name is not even referred to. Jules Marcoit. 



Cambridge, Sept. 11. 



[The series was commenced as ' Illustrated cata- 

 logue,' and not as ' Memoirs,' each number independ- 

 ently paged ; these numbers were not collected into 

 volumes until after Louis Agassiz's death, when the 

 closing number (9) of the second volume, published 

 in 1876, was entitled ' Memoirs,' and the titles to the 

 first three volumes (the third volume consisted of 

 Nos. 7 and 8) first printed and distributed. — Ed.] 



Barometer exposure. 



In accordance with ' Gan's ' suggestion in Science, 

 viii. p. 255, I herewith present a copy of the baro- 

 graph record of Blue Hill observatory for the three 

 hours from 9 a.m. to 12 m of Feb. 27, 1886. 



^AM 



IBM. 



The barograph from which this is taken is a Draper 

 barograph, and multiplies three times. Its readings 

 usually differ less than one one-hundredth of an inch 

 from the readings of an adjacent standard Hicks 

 barometer, with which its readings are compared 

 every day. The barograph is situated in the lower 

 room of a two-story tower. The air passes freely 

 from this lower to an upper room, through a register- 

 opening. In the top of this upper room is a trap- 

 door opening out on the roof. The roof is flat, with 

 a low turret around it, and the trap-door opens a 

 little to the north of the centre. A picture of the 

 observatory will be found in Science, v. p. 440. 



The wind movement during the three hours given 

 on the diagram was 55, 60, and 64 miles respectively, 

 .as shown by a Draper anemograph. The wind- 

 velocities were quite large all day of the 27th ; and 



the portion of the curve given in the above diagram 

 IS but a sample of the whole barograph curve of that 

 date, only the oscillations at an earlier hour, when the 

 wind-velocity was greater, are more rapid and 

 slightly larger, excepting the sharp depression at 

 10.20 a.m. ihis portion of the curve was selected 

 in order to exhibit this shai-p depression, which was 

 coincident with the opening of the trap-door in the 

 tower. The barograph was observed immediately 

 before and immediately after the opening of the trap- 

 door. The exact interval between opening the trap- 

 door and observing the barograph is not known, but 

 was probably less than a minute ; and I feel no doubt 

 whatever of the coincidence of the fall of pressure 

 with the opening of the trap-door. 



Several similar depressions, though not so decided 

 because the wind-velocity was less, were noted at a 

 later date, when one observer watched the barograph 

 while another opened the trap-door ; and the fall of 

 pressure coincident with opening the door was un- 

 doubted. The depression shown on the diagram at 

 11.35 A.M. is found to be coincident with a marked 

 increase in the wind's velocity, lasting several 

 minutes, followed by a more permanent increase after 

 noon. 



The following note was written on the barograph 

 sheet of the 27th, immediately after it was removed 

 from the instrument : " The sharp depression at 10.20 

 A.M. was caused by opening hatch on tower ; the other 

 sharp depressions correspond with severe gusts of 

 wind." On this date the up-and-down oscillations of 

 the mercury in the stand ard Hicks barometer were so 

 rapid that it was almost impossible to set the vernier 

 accurately. Mr. F. V. Pike informs me that he had 

 the same difficulty in reading his standard barometer 

 at Newburyport, Mass. Such oscillations of the baro- 

 graph as those on the diagram are quite common on 

 Blue Hill. They begin to be noted with wind-veloci- 

 ties of about thirty miles, and increase in range with 

 increased velocity of the wind, though winds from 

 certain directions seem to have more influence in pro- 

 ducing them than from other directions. This is 

 probably owing to the position of the apertures. A 

 rapid increase or decrease of the wind's velocity as 

 much as ten miles is, I think, always accompanied 

 here by a corresponding decrease or increase of press- 

 ure, which leads me to believe that even small wind- 

 velocities affect the barometer readings ; but the 

 small oscillations spoken of above do not occur, be- 

 cause the difference between the velocity of a gusi 

 and of a succeeding lull is not great enough to pro- 

 duce them. I see no reasons for believing that the 

 barometer is any more affected by the wind here than 

 elsewhere. ' Gan's ' statement that he found small 

 oscillations of the barograph with wind-velocities of 

 about twenty miles, a similar statement by Mr. E. B. 

 Weston of Providence, E. L, and the statement of 

 Mr. Pike that he had found rapid oscillations of his 

 barometer during the high wind of Feb. 27, con- 

 vince me that the effect of the wind on the barome- 

 ter is universal. H. Helm Clayton. 



Blue Hill meteor, observ., Sept. 2i. 



These serrations furnished by Mr. Clayton are 

 certainly very extraordinary. It will be noticed that 

 the trap-door is not upon a broad, flat roof, and also 

 that there is only one of the effects which can be 

 regarded as .05 below the general trend of the press- 

 ure trace. It seems probable that the barometer 

 suspended by long steel springs has a tendency to 

 magnify the effect. If it can be shown that the total 



