242 



SCIENCE. 



they could not fail to come in contact before vitality is 

 lost. A half hour after contact with the milt, the eggs 

 swell and become too hard to be broken by pressure of 

 the thumb and finger. Their specific gravity is now so 

 neirly equal to that of salt water that when the water is 

 at rest they float upon its surface, remain suspended in 

 the water, or occasionally sink slowly to the bottom. 

 The least current will cause them to be distributed 

 through the liquid. Mr. Earll discovered a small oil 

 globule in each egg which serves the purpose of buoying 

 it. The impregnated egg is also so transparent that the 

 fishermen, who are not usually very observing, would 

 never suspect their presence. The eggs are smaller than 

 e ?gs of almost any other species, and have an average 

 diameter of only one-twenty-eighth of an inch. It has 

 been estimated, it will be seen, that 21,952 would make 

 a cubic inch, and a quart of S7H cubic inches would 

 hold 1,267,728 eggs. 



The period of hatching is greatly influenced by the 

 temperature of the water. The average temperature dur- 

 ing the experiments at Crisfield was 84° Fahrenheit. Ten 

 hours after contact with the milt the outline of the fish 

 could be discerne 1 by the naked eye. The fish is formed 

 with the curve of the back at the lowest point ot the egg. 

 In fifteen and one-half hours, the fish began hatching. 

 In eighteen hours one-half of the eggs had hatched, and 

 in twenty hours all were out. Experiments in water at 

 78 Fahrenheit showed that twenty-four hours were nec- 

 essary for hatching. A more remarkable effect of tem- 

 perature is observable in the case of the cod. In water 

 at 45 cod have been hatched in thirteen days, but in 

 water at 31 fifty days were occupied in hatching. 



The newly-hatched mackejel are about one-eighth of 

 an inch in length, and so small as to escape through wire 

 cloth with thirty-two threads to the inch, and are almost 

 colorless. The food sac, situated well forward, is quite 

 large in proportion to the body, the anterior margin ex- 

 tending to the lower jaw. While floating on its back for 

 several hours, during its helpless condition, it passes 

 safely over the heads of its enemies, and is protected from 

 being wrecked in sand or weeds. After a few hours, be- 

 coming more vigorous, it gets to a depth of an inch or 

 more below the surface of the water. After a day or two 

 the food sac is less prominent, and the fish experiences 

 less difficulty in swimming at various depths. The young 

 mackerel hatched by Mr. Earll were so hardy that forty 

 were confined in a goblet without change of water for 

 two days before the first fish died; o.hers placed in water 

 which was allowed to cool gradually and immediately 

 transferred to water ten degrtes warmer, were not in- 

 jured in the least. In fresh water they slowly sank and 

 died in a few hours. Mr. Earll also found ihat a fair per- 

 centage o) eggs could be hatched in still water with but 

 one or two changes during their development. Eggs 

 taken at 6 P.M., and allowed to remain in a basin of water 

 till morning, when another change was made, hatched 

 with very small percentage of loss. Samples ol all the 

 different stages of development were preserved in alcohol 

 and glycerine for the National Museum. Over half a 

 million were hatched by the various methods and at vari- 

 ous times. 



The apparatus used in these experiments consisted 

 simply of floating boxes with bottoms made of wire 

 cloth. The cloth was plated with nickel to prevent in- 

 jurious ac ion of the salt water, and contained thirty-two 

 wires 10 the inch. After it was found that a lot of fish 

 had escaped through it, only the shells remaining to 

 prove that hatching had actn illy taken place, the wire 

 and eac h aperture were covered with coarse cotton cloth. 

 The boxes were provided with covers for protection 

 against storms, or wind, or rain, but were provided With 

 openings on the sides to admit fresh water from above. 



The commissioner has been intensely gratified at these 

 results due to the ingenuity el Mr. Earll, They open the 

 way to the systematic propagation of the species in waters 



where they do not now exist, and to the countless multi- 

 plication of them in the Chesapeake. The season being 

 in mid-summer will not conflict with the shad season 

 of the Spring, the salmon season of the Fall, or the cod 

 season of the Winter. The eggs are much more abund- 

 ant and hatch more easily and rapidly than those of any 

 fish now propagated. During the tour days consumed 

 in hatching a lot of shad, five lots of mackerel could be 

 hatched, and during the twenty-four days necessary to 

 hatch one lot of cod-fish, thirty-two lots of mackerel 

 would be produced. A suitable station for hatching was 

 chosen at Cherrystone, Md. The fishermen are kindly 

 disposed and will render every assistance. It is hoped that 

 young fish may be thus successfully planted as far North 

 as Narragansett Bay. 

 Smithsonian Institution, Washington, > 

 D.C., Novembct 6, 1880. S 



THE ISLAND OF MONTREAL.* 



By William Boyd. 

 A considerable portion of the waters of the Ottawa, at the 

 foot of the Lake of Two Mountains, divides on the Island of 

 Montreal. The branch that is directed to the northern part 

 of the island soon sub-divides on Isle Perrot. There 

 rapids are in each of the sub-branches. The sub-branches 

 encounter the St. Lawrence on its northern side at 

 two points, — shortly after it leaves the Cascades Rapids 

 and below Isle Perrot, from that island's inner shore. 

 The waters of the St. Law-rence bound also, indirectly, 

 the southern side of the Island of Montreal, flowing 

 in the same river-bed with the Ottawa, but beyond 

 or outside its stream. The water of the St. Lawrence 

 is greenish, that of the Ottawa reddish-brown. The 

 two rivers run side by side unmixed to the Ottawa's 

 lowermost mouth, at the foot of the Island of Montreal ; and 

 thence onward in the same manner, with increased volume 

 on the part of the Ottawa, to Lake St. Peter, where the}' 

 finally mingle. If the Ottawa should cease to exist and the 

 St. Lawrence remain, what is now the Island of Montreal 

 would probably — from the high level of the then Lake of 

 Two Mountains, and from a great fall which would, on the 

 extinction of the Ottawa, take place in the St. Lawrence 

 below the Cascades Rapids — be an island no longer ; but 

 if the St. Lawrence should disappear and the Ottawa re- 

 main, the Island of Montreal would continue to be an island 

 still. Therefore the writer is of the opinion that the Island 

 of Montreal is an island not in the St. Lawrence as has 

 heretofore been held, but in the Ottawa. 



FRIEDRICH MOHR'S LIFE AND WORKS. 

 By Dr. Geo. W. Rachel. 



On September 28, 1879, Prof. FRIEDRICH Mohr, one 

 of the greatest philosophers Germany has ever produced, 

 died after a short illness at Bonn on the Rhine. He was 

 born at Koblenz on November 4, 1806, and, therefore, at 

 the lime of his death, was nearly 73 years old. In spite of 

 this advanced age, he remained active and bright almost to 

 the very moment of death, dictating to his daughter Anna 

 until within a few hours of it in his usual clear and coher- 

 ent manner. 



His father was a pharmacist and proprietor of one of the 

 principal drug-stores of the town ; he is described as hav- 

 ing been unusually proficient in the arts of his trade, and an 

 ardent lover of his special profession as well as of science in 

 general. A wealthy man, comparatively speaking, he be- 

 stowed great care on little FRIEDRICH, the only surviving 

 child of six. The opportunity offered to the sickly, quiet 

 boy who had to be kept from school during the greater 

 part of his boyhood, was eagerly taken advantage of by him. 

 Test-tubes and retorts almost took the place of play-toys 

 with him, and Ins involuntary leisure enabled him to lay the 

 foundation for his future greatness, viz. : an ability for lab- 

 ralory work almost unsurpassed. Thus it was that his 

 method: as well as many of the instruments and apparatus 

 he devised, are found to-day in every laboratory and are used 

 all over the globe wherever chemistry has an abode. 



Ri i.l before the A. A. A. S., Hoston, iS 



