Olive Oil.--Difficulties encountered in raising an olive
crop.--Process of making Oil. 7064

IV. ELECTRICITY. ETC.--Telephony and Telegraphy on the Same
Wires Simultaneously.--4 figures. 7067

The Electric Marigraph.--An apparatus for measuring the
height of the tide.--With engravings and diagrams showing
the Siemens and Halske marigraph and the operation of the
same. 7068

Delune & Co.'s System of Laying Underground Cables.--2
figures. 7069

Electricity Applied to Horseshoeing.--Quieting an unruly
animal.--3 engravings. 7069

Esteve's Automatic Pile.--1 figure. 7070

Woodward's Diffusion Motor. 7070

V. ASTRONOMY.--Lunar Heat.--Its reflected and obscure
heat.--Trifling influence of the moon upon wind and
weather.--By Prof. C.A. YOUNG. 7073

VI. NATURAL HISTORY.--The Long-haired Pointer "Mylord."
--With engraving. 7073

VII. HORTICULTURE, ETC.--Apple Tree Borers.--Protection
against the same. 7074

Keffel's Germinating Apparatus.--With engraving. 7074

Millet.--Its Cultivation. 7074

VIII. MISCELLANEOUS.--Puerta del Sol, Madrid, Spain.--With
engraving. 7063

Dust-free Spaces.--A lecture delivered by Dr. OLIVER J.
LODGE before the Royal Dublin Society. 7067

* * * * *

PUERTA DEL SOL, MADRID.

Puerta del Sol, or Gate of the Sun, Madrid, is the most famous and
favorite public square in the Spanish city of Madrid. It was the
eastern portal of the old city. From this square radiate several of
the finest streets, such as Alcala, one of the handsomest
thoroughfares in the world, Mayor, Martera, Carretas, Geronimo. In our
engraving the post office is seen on the right. Large and splendid
buildings adorn the other sides, which embrace hotels, cafes, reading
rooms, elegant stores, etc. From this square the street railway lines
traverse the city in all directions.