delivered the opinion of the court.
Upon the trial appellee called Mr. Whelan as an expert engineer and after qualifying him by preliminary questions propounded to him the following question:
“Q. Assume that on the 6th day of February, 1900, in a certain steam power plant there were two certain boilers, that these boilers were situated in a room known as the boiler room, about fifty feet one way and eighty feet the other; that the building containing this plant was about 200 feet in length and about eighty feet in width; that there was brick partition or wall separating the boiler room from the engine room; that in the engine room were situated three engines; one in the south-east corner of that engine room and the other two engines on the north side of the engine rooms; towards the north-west corner; that these respective engines were connected with the boilers by two certain lines of pipe, one line of pipe extending to the engine in the south-east' corner and one line of pipe to the other two engines just described; that the steam was sent to the engines on the north side of the engine house and also to the other engine by two *81lines of pipe forming the segment of a circle joined and in themselves forming a bend shaped like an inverted letter “U” joined to the main pipe known as the main header; that this main header extended nearly the length of the boilers, in a straight easterly direction for a distance of about twenty-five feet; that one line of pipe went to the engine in the south-east corner and the other line of pipe went in a northerly direction and then dropping a short distance extending in a straight line through the boiler wall for a distance of about twenty feet to this first engine; this engine was connected with the main line of pipe, ten inches in diameter, by a pipe about six inches in diameter; that the extension of this line from the first engine on the north side of the power house to the next engine was eight inches in diameter, and that this eight-inch pipe was connected with the second engine by a pipe of six inches in diameter; that this line of pipe was provided with a system of bleeders or drainage; that between the boiler room and the first engine the pipe was not anchored; that between the first and second engine there were two TPs or bends in the pipe which were there eight inches; that this line of pipe and fittings were what is known as standard pipe and fittings; that they were put in there to" withstand a steam working pressure of not to exceed 125 pounds; that the engine in the corner of the engine room—the south-east corner—required a pressure of not less than 150 pounds; that on the day in question there were certain men there for the purpose of putting gaskets in certain joints or flanges upon this line of pipe leading to the two engines; on the north side of the engine house; that they had put in several gaskets, including a gasket in a flange immediately opposite Ho. 1 engine and forming the portion of the T with which the pipe extending from the ten-inch pipe connected Ho. 1 engine; that the work had been done in a proper workmanlike manner; that the joints were brought together without any undue strain on the pipe or fittings; that in the evening of that day the steam was turned on from the boilers at a pressure of about 160 pounds to the square inch; that this plant ran for about fifteen minutes *82and the steam was then shut off because of the blowing out of a gasket in a condenser or two-inch pipe in the engine in the south-east corner of the plant; that after about twenty-five to thirty-five minutes the steam was again turned on, passing through both lines of pipe; that a certain party was unable to open the header valve without assistance and that he was assisted in that by another man there; that they both ascended to the top of the boiler within a space of one and a half to two minutes, opened the by-passes and valves there, causing 160 pounds of steam to be sent through the header to the two lines of pipe; that within two or three minutes following the turning on of the steam an explosion occurred in the steam pipe in the engine room in the flange opposite the engine on the north side:—the engine nearest the boiler wall burst, and that then this line of pipe burst in other places, including the flange opposite the second engine forty-two feet to the east, and the fittings of both engines, and that following the steam there was a great volume of water surging through this pipe to such an extent that there was about four inches of water on the floor there; I will ask you, under those circumstances, taking into consideration all the facts stated in this hypothetical question, what in your opinion was the cause of the explosion ?
(Defendant objects to the question, because it contains negative propositions and is argmnentative and does not state the evidence correctly.)
Assume, also, that the gasket that was inserted in the ten-inch flange was one-eighth of an inch or more thicker than the gasket that had been removed.
The Court : Do you want to add anything to your hypothetical question ?
Mr. McGoorty : I do not, your Honor.
The Court: You may answer.
(Exception by defendant to the ruling of the court.)
*83Mr. McGoortv : The question is, what was the cause of the explosion under those circumstances ?”
The witness answered in substance that “The cause of the explosion, in my opinion, under those circumstances, was a rush of water passing through there and coming up when the valves were suddenly opened, and with the amount of condensation that had taken place in the pipe during the time that the plant was shut down after steam being first turned on caused what is known among practical engineers—because of the water hammer. In other words, the velocity of the steam in traveling through the pipe carries that water ahead; the water forms a head, a wall or plunger, filling almost the full area of the pipe.
Mr. McGoortt : Carries what water ahead ?
A. The water that is condensed in there and also the water that was drawn or siphoned over with the steam; it would form a ram, which would meet a certain amount of contraction, having a tendency to pull the pipe apart and immediately on striking an elbow or obstruction or a reduction in area of the outlet of the pipe it would form then a hammer with a pushing effect, and there would also be a counteracting or back rush, and the force of those blows are tremendous when we stop to think of it—the force of the blows is tremendous and the drip pipes put in for the purpose of carrying away ordinary condensation due to turning atmosphere into the pipes were not large enough to carry off any larger volume of water of that kind.”
It was error to permit the witness to answer the above question. It called for the opinion of the witness as to the cause of the explosion. That was a question for the jury to pass upon after they had been put in possession of the facts. I. C. R. R. Co. v. Smith, 208 Ill., 608, and cases there cited. This court considered this' precise point in City of Chicago v. Powers, 117 Ill. App. 453.
The question is also improper because it does not state all the undisputed and. important facts before the jury. It *84called for the opinion of the witness upon a system of steam pipes materially different from that shown by the evidence.
The answer of the witness was .damaging and injurious to the defendant’s case. For this error the judgment is reversed and the cause is remanded.
Reversed and remanded.