A shale shaker comprising: a basket having a front, solids discharge end and a rear, feed end spaced apart by opposed first and second sides; said basket including a stack of screen decks, each screen deck having a screening surface, with the screening surface of the screen decks spaced apart and superposed one above the other; wherein the stack of screen decks comprises at least a lower, first, screen deck and an upper, second, screen deck directly above the first screen deck, and wherein the screening surfaces (13a, 13b) of the first and second screen decks (8a, 8b) are spaced apart, by a vertical spacing of from 20mm to 250mm, at the extreme end of the feed receiving end of the second screen deck; wherein the screening surfaces (13a, 13b) of each of the first and second screen decks (8a, 8b) have a lower, feed receiving, end (10a, 10b) that is proximal to a fluid retaining wall at the rear end of the basket and a distal, higher, solids discharge end (12, 12b) at the front of the basket; wherein the feed receiving end of the second screen deck is further from the back of the basket than the feed receiving end of the first screen deck; wherein there is a cavity above the feed receiving end of the first screen deck, in direct fluid communication with the space between the screening surfaces (13a, 13b) of the first and second screen decks (8a, 8b), and only receiving feed that has passed through the upper, second, screen deck; wherein the cavity extends to higher than the extreme end of the screening surface of the second screen deck, at the feed receiving end; and wherein, in normal use, there is no outlet for solids and liquid from the cavity other than to the screening surfaces (13a, 13b) of the first and second screen decks (8a, 8b) and the space between them, and wherein the cavity is directly above the screening surface at the feed receiving end of the first screen deck and extends at least across the full width of the screening surface at the feed receiving end of the first screen deck. a basket having a front, solids discharge end and a rear, feed end spaced apart by opposed first and second sides; said basket including a stack of screen decks, each screen deck having a screening surface, with the screening surface of the screen decks spaced apart and superposed one above the other; wherein the stack of screen decks comprises at least a lower, first, screen deck and an upper, second, screen deck directly above the first screen deck, and wherein the screening surfaces (13a, 13b) of the first and second screen decks (8a, 8b) are spaced apart, by a vertical spacing of from 20mm to 250mm, at the extreme end of the feed receiving end of the second screen deck; wherein the screening surfaces (13a, 13b) of each of the first and second screen decks (8a, 8b) have a lower, feed receiving, end (10a, 10b) that is proximal to a fluid retaining wall at the rear end of the basket and a distal, higher, solids discharge end (12, 12b) at the front of the basket; wherein the feed receiving end of the second screen deck is further from the back of the basket than the feed receiving end of the first screen deck; wherein there is a cavity above the feed receiving end of the first screen deck, in direct fluid communication with the space between the screening surfaces (13a, 13b) of the first and second screen decks (8a, 8b), and only receiving feed that has passed through the upper, second, screen deck; wherein the cavity extends to higher than the extreme end of the screening surface of the second screen deck, at the feed receiving end; and wherein, in normal use, there is no outlet for solids and liquid from the cavity other than to the screening surfaces (13a, 13b) of the first and second screen decks (8a, 8b) and the space between them, and wherein the cavity is directly above the screening surface at the feed receiving end of the first screen deck and extends at least across the full width of the screening surface at the feed receiving end of the first screen deck.