SOMERVILLE, J.

The evidence was sufficient to carry to the jury the question of the causation of the fire by sparks emitted from defendant’s engine.

[1J Defendant’s evidence showed that the engine in question was properly constructed and equipped, in good repair, and properly operated and managed. This was a complete defense in this case, unless that showing was contradicted as by evidence that the sparks emitted on this occasion were of unusual size, or in unusual quantities, or were thrown an unusual distance, in which case it was for the jury to say whether the construction, equipment, repair, and management, one or all, were proper and sufficient. Coffman v. L. & N. R. R. Co., 184 Ala. 474, 63 South. 527; L. & N. R. R. Co. v. Stanley, 186 Ala. 95, 65 South. 39; Farley v. M. & O. R. R. Co., 149 Ala. 557, 42 South. 747.

[2] One of plaintiff’s witnesses testified that the sparks here emitted were unusual in size and quantity; and another testified that they were in quantities larger than he had observed from other engines running at night. “Unusual” is a word of comparison. Comparisons are obviously wanting in probative value unless relative conditions are substantially the same. The evidence here shows, and this is but common knowledge, that the quantity of sparks emitted by an engine will depend upon the force and rapidity of the exhaust, and this in turn is dependent upon the load to be pulled, as well as upon the grade and curve of the track. Manifestly the quantity and size of sparks emitted by a heavily loaded engine pulling up a grade would be unusual with respect to an engine pulling a lighter load on a level track, or on a down grade; ■ but it might not be unusual with respect to any engine operated under equally unfavorable conditions.

[3] The engine in this case was heavily loaded with freight cars, and was pulling up grade on a .curve. Under such- conditions I think the witness Johnson’s statement that it emitted an unusual quantity of sparks, as compared with any other engines in general as observed by him, was not prima facie relevant, and should have been excluded by the trial court. See L. & N. R. R. Co. v. Mar- *221 bury L. Co., 125 Ala. 237, 259, 260, 28 South. 438, 50 L. R. A. 620. Without conceding that this testimony was obnoxious to any objection, a majority of the court hold that the objection on the ground of irrelevancy was not apt as an objection to the comparison made by the witness, and was properly overruled.

[4] The instructions given to the jury at the request of defendant fully covered the law of the case, including the several refused charges, and were in some respects more favorable to defendant than a strict adherence to the law would require.

It results that the judgment must be affirmed. ,

Affirmed.

ANDERSON, C. J., and McCLELLAN, SAYRE, and GARDNER, JJ., concur. SOMERVILLE and THOMAS, JJ., dissent on the single question of the admissibility of the testimony of the witness Johnson,