REPORT OF COMMISSIONER OF FISH AND FISHERIES. 129 



organisms was thus obtained. Those collected in 1889 have been re- 

 ported upon by Prof. W. K. Brooks, in the paper of Prof. Libbey above 

 cited, and the material subsequently taken has been referred to Prof. 

 Brooks and others for examination. During the first summer Prof. 

 Magie took advantage of the opportunity afforded to secure a set of 

 observations on the electric conditions of the atmosphere, which have 

 also been published in Prof. Libbey's report. 



Southern mackerel-grounds. — From May 5 to June 8, 1891, the schooner 

 Orampus was engaged in making a series of observations over the 

 mackerel grounds, from Delaware northward to Massachusetts. This 

 was in continuation of similar inquiries made in previous years to de- 

 termine so far as possible the temperature and other physical phenom- 

 ena connected directly with the northerly movement of the advance 

 schools of mackerel along the coast. As is well known, these fish 

 first make their appearance inside of the warm waters of the Gulf 

 Stream at a variable distance north of Capo Hatteras, and work thence 

 northward or approach the shores at successively more northern lati- 

 tudes. The first schools have generally been seen the very last of 

 March or early in April, and previous to the enactment of the law pro- 

 hibiting the use of i)urse seines before June 1, the fishing vessels were 

 accustomed to anticipate their coming with nuich eagerness, making 

 diligent search for them, and subsequently following the fish during 

 their migrations. In her former cruises over these grounds the Grampus 

 was greatly aided by the jiresence of these vessels, which, scattered 

 over a rather wide area, made it difficult for any schools offish to pass 

 unnoticed. During the last season, however, her work was necessarily 

 carried on without this very material assistance. 



The principal object of the cruise was to locate the early schools of 

 mackerel, to follow their movements northward or in whatever direc- 

 tion they might take, and to learn everything possible regarding the 

 conditions of the air and water in connection with their habits. As it 

 was somewhat late in the season before the trip began it was expected 

 that the schools were already upon the grounds, and that it would not 

 be necessary to proceed very far south before meeting them. Such was 

 found to be the case, but the observations were carried southward from 

 Woods Holl until the fish were encountered, and thence over a part of 

 the area through which they had passed, in order to obtain the neces- 

 sary data for com^jaring the conditions in advance of the first schools 

 with those existing in their rear. Subsequently the Grampus followed 

 the schools as far as Marthas Vineyard, taking ripe males the last of 

 May and ripe females the first of June, in that vicinity. The physical 

 observations have not yet been reduced and compared. 

 H. Mis. 113 9 



