172 



SCIENCE. 



the pole of the field-magnets. In such machines the mo- 

 tion of the poles of the armature is also more in a line, co- 

 incident with the line of attraction as exercised between the 

 two systems of poles ; while in machines with field-magnets 

 of two poles only the motion of the poles of the armature 

 is at times at angles of 45 degrees to one degree from the 

 direct pull. 



I may, perhaps, be allowed to call attention to another 

 matter of importance, awaiting further research. We find 

 that in the three types of dynamo-machines, as constructed 

 by Siemens, Gramme and Wilde, the relative positions of 

 the axes of the field-magnets and those of the armatures are 

 altogether different. Yet the three systems work well. 

 We are unable, however, to state with certainty which po- 

 sitions of the axes are the best, or why any one of these 

 positions should be better than the others, and in the face 

 of experience, the theory of tubes or lines of force is little 

 more than a hypothesis, with all its diffusion, vagueness 

 and uncertainty. 



Having so far considered general principles chiefly, I now 

 beg to describe this motor (Fig. 5). A B C D is a wooden 

 baseboard, EFGHa frame, consisting of the two parallel 

 round rods F E and G H, and the two flat bars F G and 

 E H, made of the best wrought iron, and carefully soften- 

 ed. The four bars are screwed together at the corners, and 

 supported by four brass brackets over the baseboard. These 

 inner rods form the compound core of the field magnets, 

 a combination, as it were, of two horseshoe magnets, whose 

 similar poles (S S and N N) form the junctions. Thus we 

 have practicallv two poles only, a S and a N pole. Six coils 

 of insulated copper wire are wound over the different por- 

 tions of this core, shown in the drawing ; the active pole- 

 pieces are left exposed for a long distance, bearing no coils, 

 The spindle P L, which carries a Siemens armature of the 

 old form, or an armature with a compound tubular core ; 

 the commutator and pulley traverses the flat crossbar F H. 

 The core of the armature is made of sheets of charcoal-iron, 

 and it bears a coil of stout insulated copper wire. The com- 

 mutator is of the ordinary kind, consisting of two half-tubes 

 of brass, insulated from each other and from the spindle, and 

 each forming one of the terminals of the coil. Fig. 2 

 represents a sectional view of a compound machine, acting 

 on the same principles ; Fig. r is a view of the two-end 

 castings which hold the field-magnet. This machine con- 

 tains a system of six field-magnets and six poles, and a 

 compound armature with six poles. The current is to be 

 reversed six times for each revolution, and to accomplish 

 this I have devised the following commutator (see Fig. 8) : 

 — In these machines, also, the poles of the field-magnets or 

 those of the armature may be of such a shape as to be 

 nearly always approaching to, or receding from, each other, 

 while in active motion. 



The development of most important machines is destined 

 to reach a certain stage of perfection, when further improve- 

 ments cannot be accomplished by the inventor unaided ; 

 the second and important factor needed then is the co-op- 

 eration of inventive and investigative talent with capital. 

 This stage of perfection has been reached in the steam- 

 engines, gas-engines, printing-machinery, etc., and it may 

 be said to be rapidly approached by the progress made in 

 dynamo-machines and electro-motors. 



The development of the latter machines is followed by 

 the scientific world with greater interest, and it evokes 

 more eager expectations than that of other machinery, 

 chiefly because it is not, and cannot be, identified with the 

 solution of a problem limited within the confines of mechan- 

 ical difficulties and commercial interests, but necessitates 

 a further and deeper investigation into that great and subtle 

 power, electricity, whose manifestations are so striking in 

 their effects, so mysterious in their nature, so promising of 

 great results in an immediate future, so fertile a field of re- 

 search to the pioneer of science. 



BRITISH ASSOCIATION FOR THE ADVANCE- 

 MENT OF SCIENCE. 1880. 



Till. British Association f"i the Advancement of Sri. q< . 



met ;it Swansea on the 4th of Septembei last, under the 

 president \ of Dr. Ramsi y, who look ;is the subject of his 

 address, "The Recunence of Certain Geological Pheno- 



mena in Geological Time." His object appeared to be to 

 show that all known geological formations have been pro- 

 duced under physical circumstances closely resembling, if 

 not identical, with those with which we are more or less 

 familiar. Through the various geological epochs he traced 

 this identity of operations in respect to the metamorphism 

 of rocks, the products of volcanoes, the upheaving and de- 

 nudations of mountain chains, the deposit of great inland 

 areas of salt, a recurrence of fresh-water conditions in lakes 

 and estuaries, and glacial influences. His conclusion was 

 that from the Laurentian epochs down to the present day 

 all physical events in the history of the earth have varied 

 neither in kind nor in intensity from those of which we now 

 have experience. 



The conclusions drawn from this address are summed 

 up in the closing words of Professor Ramsey's discourse, 

 as follows: 



'• In opening this address, I began with the subject of 

 the oldest metamorphic rocks that I have seen — the Laur- 

 entian strata. It is evident to every person who thinks on 

 the subject that their deposition took place far from the be- 

 ginning of recognized geological time. For there must 

 have been older rocks by the degradation of which they 

 were formed. And if, as some American geologists affirm, 

 there are on that continent metamorphic rocks of more 

 ancient dates than the Laurentian strata, there must have 

 been rocks more ancient still to afford materials for the de- 

 position of these pre-Laurentian strata. Starting with the 

 Laurentian rocks, I have shown that the phenomena of 

 metamorphism of strata have been continued from that 

 date all through the later formations, or groups of 

 formations, down to and including part of the Eo- 

 cene strata in some parts of the world. In like 

 manner I have shown that ordinary volcanic rocks 

 have been ejected in Silurian, Devonian, Carboniferous, 

 Jurassic, Cretaceo-ooliiic, Cretaceous, Eocene, Miocene, 

 and Pliocene times, and from all that I have seen or read 

 of these ancient volcanoes, I have no reason to believe that 

 volcanic forces played a more important part in any period 

 of geological time than they do in this our modern epoch. 

 So, also, mountain chains existed before the deposition of 

 the Silurian rocks, others of later date before the Old Red 

 Sandstone strata were formed, and the chain of the Ural 

 before the deposition of the Permain beds. The last great 

 upheaval of the Alleghany Mountains took place between 

 the close of the formation of the Carboniferous strata of 

 that region and the deposition of the New Red Sandstone. 

 According to Darwin, after various oscillations of level, 

 the Cordillera underwent its chief upheaval after the Cre- 

 taceous epoch, and all geologists know that the Alps, the 

 Pyrenees, the Carpathians, the Himalayas, and other moun- 

 tain chains (which I have named) underwent what seems to 

 have been their chief great upheaval after the deposition of 

 the Eocene strata, while some of them were again lifted up 

 several thousands of feet after the close of the Miocene 

 epoch. The deposition of salts from aqueous solutions in in- 

 land lakes and laeoons appears to have taken place through 

 all time — through Silurian, Devonian, Carboniferous, Per- 

 mian, Triassic, Jurassic, Cretaceous. Eocene, Miocene, and 

 Pliocene epochs — and it is going on now. In like manner 

 fresh-water and estuarine conditions are found now in one 

 region, now in another, throughout all the formations or 

 groups of formations possibly from Silurian times onward ; 

 and glacial phenomena, so far from being confined to what 

 was and is generally still termed the Glacial Epoch, are 

 now boldly declared by independent witnesses of known 

 high reputation, to begin witli the Cambrian epoch, and to 

 have occurred somewhere, at intervals, in various forma- 

 tions, from almost the earliest Paheozoic times down to our 

 last post-Pliocene "Glacial Epoch " 



If the nebular hypothesis of astronomers be true (and I 

 know of no reason why it should be doubted), the eartli was 

 at one time in a purely gaseous state, and afterwards in a 

 fluid condition, attended by intense heat. By and by con- 

 solidation, due to partial cooling, took place on the sur- 

 fate, and as radiation of heat went on the outer shell thick- 

 ened. Radiation still going on, the interior fluid matter 

 decreased in bulk, and, by force of gravitation, the outer 

 shell being drawn towards the interior, gave way, and, in 

 parts, got crinkled up, and this, according to cosmogonists, 



