1. In a cable-type coring apparatus comprising a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing, and means for retrieving the head with a cut core therein; the improvement in which said coring head comprises coaxial upper and lower tubes slidable relative to each other, said upper tube having lateral openings therethrough and an elastic deformable sealing ring encircling said upper tube above said lateral openings and in slidable sealing relationship with the interior of said string of tubing, said lower tube having lateral openings therethrough that move into and out of registry with said lateral openings through said upper tube upon sliding movement of said upper and lower tubes relative to each other, at least one latch pivotally mounted on said lower tube for swinginG movement about a horizontal axis, said at least one latch being disposed between portions of said upper tube, said latch having a cam slot therein, and means on said portions of said upper tube engageable in said cam slot selectively to move said at least one latch about said horizontal axis upon relative movement between said inner and outer tubes.

2. In a cable-type coring apparatus comprising a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing and means for retrieving the head with a cut core therein, the improvement in which said coring head comprises: a coaxial upper tube (21) having: a transversely closed section (24) lateral openings (22) above said closed section (24) two elongated longitudinal slots (28, 29) diametrically opposed under the closed section (24) a diametral uncoupling pin (34) under said closed section (24) and an annular projection (23) extending outwardly above the lateral openings (22), an annular sealing ring (40): carried by the upper tube (21) displaceable therewith and sealingly engaged within the tubing (4), a coaxial lower tube (14), said upper and lower tubes (14, 21) being slidable relative to each other, said lower tube (14) partially surrounding the upper tube (21) having lateral openings (38) located at its upper end and radially facing the lateral openings (22) of the upper tube (21) when the lower tube (14) abuts against the annular projection (23) of said upper tube (21) having two elongated longitudinal slots diametrically opposed perpendicular to the elongated slots (28, 29) of the upper tube (21) and located under the lateral openings (38) carrying an axle (27) extending through the elongated slots (28, 29) of the upper tube (21) two latches (25, 26) pivotally mounted on the axle (27) of the lower tube (14) forced outwardly by a spring (33) engaged through the elongated slots of the lower tube (14) engageable in a recess (9) of the tubing (3, 4) to be stationary therein having uncoupling slots (35, 36) partly facing each other and transversed by the uncoupling pin (34) of the upper tube (21) a spring (30) connecting both upper and lower tubes (14, 21) and resiliently forcing them to slide towards each other, so that: during the downward movement of the head under the action of fluid pressure, the upper tube (21) with its closed section( (24) and its sealing ring (40) with its lateral openings (22) obturated by the lower tube (14) acts as a piston until the latches (25, 26) engage in the coupling recess (9) of the tubing (3, 4), whereby the upper tube (21) moves farther downward within the stationary lower tube (14) under the influence of the spring (30) and the fluid pressure so that the lateral openings (38 and 22) of both upper and lower tubes (14, 21) face one another and fluid under pressure flows to the coring bit (6) and, during the upward movement of the head, the upper tube (21) drives upwardly the lower tube (14) whereby the latches are moved inwardly by the uncoupling pin (34).