On the line from Madrid to Saragossa, the length of which is 213 miles, there are twenty-six tunnels; the most important of them is Horna, 1,010 metres. The total length of these twenty-six tunnels is 4,791 metres, or 3⅝ miles. On the Manzanares to Cordova Line, the length of which is 243½ kilometres, there are thirteen tunnels, the longest of which is 1,025 metres; their total length 3,092 metres. The Albaceta to Carthagena Line, is 154 miles long; the chief tunnel is that of Almadenes, along the gorge of the same name, its length is 1,056 metres. There are four short tunnels on this line, all in the vicinity of the gorge; their combined length is only 393 metres, making, with the tunnel of Almadenes, 1,449 metres. The Northern of Spain—Madrid to Irun—is 399 miles long. Although it is not the longest, it is probably the most important railway in Spain, traversing nearly throughout its entire extent, a difficult, and, at places, an extremely hilly country, and finally terminating at the Pyrenees, where it meets the Bayonne and Irun Railway. Thus, on the section from L’Escurial to Avila, 44 miles long, there are sixteen tunnels, the total length of which is 4,408 metres, all of which are associated with numerous extremely difficult works of art in their immediate vicinity, some of the viaducts varying from 95 to 135 feet in height, with other proportional dimensions. It is in this section that the Guaddarama Mountains are traversed, and, until the locomotive crossed the Mont Cenis the summit of this railway was the highest in Europe, 4,505 feet above sea level. On the section between Otzaurte and Beasain, 33 miles long, there are twenty-three tunnels, the total length of which is 10,351 metres. Some of the works of art on this section are magnificent in their character and construction. The tunnels on the other sections of the line are not so numerous; nevertheless, they are altogether fifty-eight in number, with an aggregate length of 22,160 metres, exactly 14 miles. Turning from the most difficult Spanish railway in point of construction, to the easiest for the greater part of its extent, the Seville, Xeres and Cadiz Line, the length of which is 103 miles, we find that there are no tunnels upon it, although on the section between Xeres and Cadiz there are several extremely difficult works of art. The Alar del Rey to Santander Railway is 87 miles long. It has twenty-one short tunnels upon it, the total length of which is 4,808 metres. The length of the Palencia and Astorya Line is 110 miles. It runs from Palencia to Gigon, on the Bay of Biscay. This railway is only in course of construction. There are several tunnels upon it, of which the particulars have not yet been published.