TRANSACTIONS OF THE SECTIONS. 27 
‘true that it has many minute perforations, but by laying on at least six thicknesses 
between each layer of wire perfect insulation is secured. The greatest care must be 
taken in protecting the ends of the layers so as to prevent the sparks passing from 
one to the other. The condenser should be at least fifty sheets of tinfoil of about 
1 square foot in size, These sheets must be separated from each other by three 
sheets of varnished paper or gutta-percha tissue. Every alternate sheet of foil is 
conected together, thus forming two poles, to be attached one to each side of the 
break. It may be placed at the bottom of the stand or in a separate box,—the latter 
I prefer. In developing the power of the machine, everything depends upon the con- 
tact breaker, which should be capable of retaining contact until the whole of the mag- 
netism is obtained, and capable also of breaking contact as soon as the smallest 
quantity is induced. These results are obtained in the break attached to this instru- 
ment. ‘The hammer is made to vibrate freely between the iron core and the coil, and 
the brass screw terminating with the platinum plate at the back of the hammer : a very 
small amount of magnetism will be sufficient to attract the hammer, and so break 
the contact. If, now, I bring this screw (placed half-way up the spring carrying the 
hammer) to bear upon the spring, it will have’the effect of pressing the two platinum 
plates together, so that it takes a greater amount of magnetism to separate them. 
By this means I can regulate the power of the instrument to the purposes for which 
it is required. The battery 1 employ is a five cells of ‘‘ Grove’s,” with immersed 
platinum plates 5 X 3, having an exposed surface of 140 square inches. With such a 
battery and a coil thus constructed, I can always ensure sparks from half an inch to 
4 inches in air. The machine now exhibited contains six miles of wire, and, worked 
with the same battery, gives 64-inch sparks. The position which the induction coil 
is now taking in this electrical age is one of considerable importance. It has awakened 
new philosophical ideas, and is being successfully applied to practical purposes of 
the highest advantage to mankind. For blasting purposes, a three-mile coil is capa- 
ble of firing fifty charges simultaneously. But important as its present position is, 
and successful as its past application has been, there can be little doubt that machines 
can be constructed that will obviate the necessity for employing such ponderous 
machines, and still more ponderous batteries that have been at work on the Atlantic 
Cable. 
— 
On the Magnetic Dip at Stockholm. 
By Dr. F. A. Sirsestrém, of Stockholm. 
Later observations on the magnetic dip at Stockholm confirm the known fact that 
this magnetic element has a minimum in the winter, 
ASTRONOMY. 
On the Perihelia and Ascending Nodes of the Planets. 
By Enwarp Josuua Cooper, F.R.S. 
It is known to many that my attention has been called to the distribution, in helio- 
centric longitude, of the perihelia and ascending nodes of the planets since the year 
1850, In 1851, the then results were published by me, in my Preface to ‘Cometic 
Orbits,’ Since that period [ communicated the further results, arising from subse- 
uent discoveries of asteroids, to the Royal Astronomical Society and the Royal 
ociety, The last notice which I communicated to the Royal Society was in the 
last year, when the number of known planets was 51. This notice was accompanied 
by diagrams of their positions. At present there are 62; but no elements of the last 
haye been yet, I believe, computed. Taking, then, 61 of these, we find that the 
perihelia of 42 are found in the semicircle of heliocentric longitude, between 0° and 
180°, and only 19 in the other semicircle. With reference to the ascending nodes 
of the 60 planets, 42 are likewise found between 0° and 180°, and only 18 in the 
remaining semicircle, But the accompanying Table will show some more remark- 
able results, viz. that when there were only 4 known asteroids and 7 large planets, 
