SCIENCE. 
172 
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, E F G II a frame, consisting of the two parallel 
round rods F E and G H, and the two flat bars F G and 
E II, made of the best wrought iron, and carefully soften- 
ed. The four bars are screwed together at the corners, and 
supported bv 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 practically 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 II. 
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 otherand 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. 1 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. 
Tiie British Association for the Advancement of Science 
met at Swansea on the 4th of September last, under the 
presidency of Dr. Ramsey, who took as the subject of his j 
address, “ The Recurrence of Certain Geological Pheno- j 
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 metamotphic 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 lagoons 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 with the Cambrian epoch, and to 
have occurred somewhere, at intervals, in various forma- 
tions, from almost the earliest Palseozoic 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 earth 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 pHce 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, 
