SUPPLEMENT. 



9 



operating the machine. It has been my purpose to add to the sounding- 

 machine, when warranted by economy, every appliance which may save 

 time or prevent accident. In many localities there is but a small propor- 

 tion of weather during which astronomical observations can be had for 

 determining the positions of soundings; it is therefore highly important in 

 such localities to make the best use of favorable weather. 



GRAVITATING OR COLLECTING TRAP FOR OBTAINING ANIMAL SPECIMENS FROM INTER- 

 MEDIATE DEPTHS. 



In the original volume, page 144, last paragraph, and page 145, foot- 

 note, reference is made to the invention of an apparatus for collecting 

 animal forms from intermediate depths. The apparatus has now been well 

 tried and a full description of it by myself (accompanied by a drawing), 

 and a statement of the results obtained, by Prof. Alexander Agassiz, is 

 contained in the "Bulletin of the Museum of Comparative Zoology at 

 Harvard College, Vol. VI, Nos. 8 and 9, September, 1880." 



I quote a part of my own description contained therein, as follows: 



"The old practice of dragging for animal forms at intermedial depths 

 by means of a tow-net, which, during the several operations of lowering, 

 dragging, and hauling back remained open, was not regarded by Prof. 

 Alexander Agassiz as affording acceptable evidence of the habitat of such 

 specimens as were obtained, and he frequently referred to the subject 

 during our association on board the "Blake"* in 1878. 



"In March, 1880, it having been arranged that Professor Agassiz 

 should make another cruise on board the "Blake," Commander J. R. 

 Bartlett, U. S. N., commanding, he asked my co-operation in devising an 

 apparatus to meet the rigid demands of the work in question. This 

 resulted in the apparatus described herein, which is presented in the pre- 

 cise form used with success by the "Blake," although, as may readily be 

 seen, it is open to great improvement, especially in minor details. 



"The 'Challenger' had examined intermediate depths by means of 

 tow-nets trailing from the dredge-rope while hauling the dredge or trawl. 

 In such a practice it must have been that the depths to which the nets 



