Opinion by
This case involves the correctness of the assessment levied against the taxable real estate of the Jones and Laughlin Steel Corporation situate in the Borough of Aliquippa, Beaver County, Pennsylvania.
In 1955, the county commissioners directed a reassessment of all taxable real estate within the territorial boundaries of the county. They engaged the services of Cole-Layer-Trumble Company, an appraisal firm from Dayton, Ohio, to conduct the necessary reappraisals. 1 In 1958, the appraisal was completed and adopted by the Board of Assessment and Bevision of Taxes as the basis for county tax assessments for the year 1959. As a result, the assessed valuation of real estate of the Jones and Laughlin Steel Corporation, located in the Borough of Aliquippa, was reduced from the sum of $21,365,945 to $17,528,400. The further result was to shift 22.8% of the total reаl estate assess *425 ment of the borough from the corporation to other taxpayers.
The Borough of Aliquippa appealed from the board’s assessment to the court of common pleas. The steel corporation, and the school district of the borough, were permitted to intervene. The court dismissed the appeal. From that order, the borough and the school district appealed.
Beaver County is а fourth class county and in assessing taxable real estate within its territorial limits is governed by the Act of May 21, 1943, P. L. 571, as amended, 72 PS §5453.101 et seq. Section 201 of the Act of 1943, provided as follows: “The following subjects and property shall as hereinafter provided be valued and assessed and subject to taxation for all county, borough, town, township, school (except in cities) poor and county institution district purposes, at the annual rate, (a) All real еstate, to wit: Houses, buildings, lands, lots of ground and ground rents, mills and manufactories of all kinds, and all other real estate not exempt by law from taxation.”
Under this statute, as then written, in levying the tax against a steel mill such as the one involved, the mill itself and all things included in the operation, whether fast or loose, which necessarily constituted an integral part, were valued and assessed as realty. This was the established practice under the law. See,
Mеssenger Publishing Co. v. Allegheny County Board of Property
Assessment,
Appeals and
Review,
However, Section 201 of the Act of 1943, was amended twice by the 1953 session of the Pennsylvania Legislature. 2 It is with these amendments that we are now concerned, specifically, (1) the correctness of the construction and application thereof and (2) their constitutionality.
The Amendment of July 17, 1953, added the following to Section 201: “Machinery, tools, appliances and other equipment contained in any mill, mine, manufactory or industrial establishment shall not be considered or included as a part of the real estate in determining the value of such mill, mine, manufactory or industrial establishment.” 3
The amendment of July 28, 1953, further added this: “Provided, That the exclusion of such machinery, tools, appliancés and other equipment, in so determining the value of such mill, mine, manufactory or industrial establishment, shall be postponed and shall not become effective until such real estate is valued and assessed for taxes to be levied for the tax or fiscal years beginning on or after the first day of January, one thousand nine hundred fifty-six.”
The Aliquippa Works of the steel corporation involved is a large integrated industrial establishment, *427 equipped to turn the basic raw materials of coal and iron into steel of all sizes and forms, as well as to handle all by-products which develop during the process. The steel making process is one involving the handling of materials whose weight is measured in tons. Of necessity, most of the equipment used in the operation is large, heavy, and securely anchored with solid foundations.
In determining which portions of the steel plant constituted “machinery”, etc., and were thus excluded from real estate taxation under the amendment of July 17,1953, supra, the appraisers included in this category all items which were necessary in the manufacturing process, as well as the foundations and structures directly related to such equipment and facilities. The board of assessors followed this policy. The lower court ruled this to be correct. As a result, foundations supporting, and structures enclosing, coal bins, convеyor systems, magnetic separators, bucket line elevators, coke ovens, blast furnaces, convertors and other similar heavy machinery incident to a steel mill, as well as the machinery itself, were classified as excluded from real estate taxation. Hence, the substantial reduction in the assessed valuation. The basic reasoning was that the foundations and structures were vital and necessary to the operation оf the machinery; that they constituted an integral part thereof and added nothing to the value of the real estate itself, regardless of the fact that, in most instances, the structure and foundations were permanently affixed to the land and could not be removed without material damage thereto.
The appellants argue that this constituted an incorrect interpretation of the 1953 statute and an illegal application оf the machinery exemption. It is their prime position that, while the legislature intended to abolish the “assembled industrial plant doctrine” because of its obvious injustice in fixing unattached ma *428 chinery and equipment as part of the realty for tax purposes, the legislature did not intend to exempt from real estate taxation permanent improvements to the land, i.e., things so affixed that they cannot be removed without material damagе to the land itself. In substance, it is argued that the legislature intended to adopt the common law doctrine of fixtures in the determination of what is real estate for tax purposes.
Thei’efore, the present issue boils down to this: Does the common law doctrine of fixtures determine whether or not permanent or semi-permanent improvements, (such as those excluded from the assessment) which are a contributing link in the chain of proсess to attain the desired end products in any industrial establishment, come within the meaning of “machinery, tools, appliances and other equipment” in the 1953 amendment? To this question, the answer, in our opinion, is “no.”
Appellants’ proposed method has been rejected time and again by this Court as unrealistic and impossible in application. In
Gulf Oil Corp. v. Philadelphia,
The intention of the legislature was clearly to abolish the tax ou all parts of the machinery by removing machinery from real estate taxation, and with good reason. Today most states and communities in this country are engaged in a fight to encourage new industry to move into that state or community and to retain the industries they already have. In the early 1940’s many Pennsylvania communities, such as the City *430 of Scranton, founded nonprofit corporations to achieve the before-mentioned purposes. Recently, the state government, through a newly formed Pennsylvania Industrial Development Corporation, has delved into this expanding tussle over jobs and industry by granting loans to the community corporations to aid them in this fight. It is obvious that the legislature was aware of these activities since it has been appropriating large sums of money to the industrial development corporation. But the legislature also realized that building new factories at low interest rates wasn’t enough to compete with other states which also offer low tax rates to industry, and therefore, it gave needed tax relief to industry in Pennsylvania. This effort has taken several forms: (a) For example, corporations organized for manufacturing purposes were declared exempt from the annual tax on their capital stock: Capital Stock Tax Act of June 1, 1889, P. L. 420, §21, as amended, March 15, 1956, P. L. (1955) 1285, §1, 72 PS §1871; (b) Again, no taxes have been permitted under the general mercantile tax “on any privilege, act оr transaction related to the business of manufacturing . . . .” Act of June 25, 1947, P. L. 1145, §1, 53 PS §6851; (c) Again, in 1911, “machinery of all kinds” was excluded from real estate taxation in Pittsburgh.. Act of May 12,1911, P. L. 287, §1, 53 PS §23104; (d) In 1915, a similar exclusion was passed to exclude from taxation in Philadelphia County “the machinery and tools used in manufacturing in any mill or manufactory.” Act of June 3, 1915, P. L. 787, No. 346, §1, 53 PS §15976; (e) and finally, the 1953 amendments to The Fourth to Eighth Class County Assessment Law. As we stated in interpreting the Act of June 3, 1915, in Gulf Oil Corp. v. Philadelphia, supra, at 119, “Article IV, section 51, оf the Statutory Construction Act states that ‘the intention of the Legislature may be ascertained by considering, among other matters — (1); (2); (3); *431 (4) the object to be attained.’ The ‘object’ of the Act of 1915 was to attract to this state manufactories and to retain those whose owners might be tempted to move them to states with more liberal tax policies.” Therefore, it is self-evident from a study of the history of tax legislation in Pennsylvania that the “object to be obtained” by the 1953 amendments was to provide tax relief for Pennsylvania industries by removing all integrated “machinery, tools, appliances and other equipment” from the real estate tax.
The Act of 1915, supra, construed in Gulf Oil Corporation v. Philadelphia, supra, excluded “machinery and tools used in manufacturing.” 5 The Act of 1953 excludes “machinery, tools . . . contained in any mill 6 . . . Appellants contend that the words “contained in” are more restrictive than the words “used in.” To us, it appears that the contrary is correct. Certainly a piece of machinery must be contained in the manufacturing plant befоre it can be used. The reason for substituting the phrase “contained in any . . . industrial establishment” for “used in manufacturing” was apparently to avoid the technical question as to what constitutes processing or manufacturing as the Gulf Oil Corporation case presented.
Therefore, it is our considered conclusion, under the statute involved, improvements, whether fast or loose, which are used directly in manufacturing the products that the establishment is intended to produce and are neсessary and integral parts of the manufacturing process and are used solely for effectuating that purpose, are excluded from real estate assessment and taxation. On the other hand, improvements which benefit the land generally and which may serve various users of the land, are not in this category. Neither are struc: *432 tures, which are not necessary and integral parts of the manufacturing process and which are separate and apart therefrom, within the exclusion. A structure used for storage, for example, is part of the realty and subject to real estate taxation.
Although, we cannot review and discuss in this opinion each and every item involved herein, two, specifically, need discussion. They are the loading docks for both coal and pig, and the quinching towers for the coke ovens. The loading docks cannot, under any extension of meaning, fit into “machinery, tools, appliances and other equipment” as the court below concluded. They are real estate. But, on the other hand, the quinching towers are an absolutely necessary part of the process in making coke and, therefore, come within the definition of machinery.
The appellants also contend that the machinery exemption should be declared invalid because the act contains no definition of the words, “machinery, tools, appliances and other equipment” and is, therefore, so vague, indefinite, or inconsistent, that it is incapable of interpretation, application or enforcement. Keeping the legislative purpose in mind, we cannot agree. These words of exclusion are obviously clearer and broader than the Act of June 3, 1915. As pointed out before, in the latter act “maсhinery . . . used in manufacturing” were the key words, while in the 1953 amendment, “machinery, tools, appliances and other equipment contained in any . . . industrial establishment” are the words in question. The legislature was obviously aware of this Court’s decision interpreting the word “machinery” in the Act of 1915. See, Gulf Oil Corp. v. Phil adelphia., supra. “In ascertaining the intention of the Legislature in the enactment of a law, the courts may be guided by the following presumptions among others: . . . (4) That when a court of last resort has construed the language used in a law, the Legislature in subse *433 quent laws on the same subject matter intend the same construction to be placed upon such language.” Act of May 28, 1937, P. L. 1019, §52, 46 PS §552.
The appellants further contend that the Amendments of 1953, supra, contravene Art. IX, § §1 and 2 of the Pennsylvania Constitution in that they exempt property from taxation and permit lack of uniformity in taxation. The pertinent part оf Section 1 provides: “All taxes shall be uniform, upon the same class 7 of subjects, within the territorial limits of the authority levying the tax . . . .” Section 2 provides: “All laws exempting 8 property from taxation, other than the property above enumerated shall be void.”
What is overlooked in this argument is that the Act of 1953 doesn’t create an exemption but creates an exclusion — that being excluded is the concept of the assembled industrial plant doctrine as a determining factor in The Fourth to Eighth Class County Assessment Law. The legislature clearly stated that it was creating an exclusion. The Act of July 17, 1953, P. L. 455, states that these items “shall not be considered or included.” The Act of July 28, 1953, P. L. 703, states that the “exclusion 9 of such machinery, tools, appliances and other equipment . . . shall be postponed . . . .” Therefore, it is obvious that the legislature, by this act, merely moved “machinery, tools, appliances and other equipment”, which had by judicial interpretatiоn been classified with real estate, into a separate class.
Section 1 of Art.
IX
of the Pennsylvania Constitution provides that all taxes shall be uniform upon the same class of subjects. Classification is an integral part of any discussion of uniformity. It is in fact the basis of uniformity. Classification is a legisative de
*434
termination and so long as there is a valid basis for the classification, it will be sustained. As was stated in
Coe v. Duffield,
It is obvious that the classification in question is reasonable and well grounded upon consideration of public policy. And as we stated in
Jermyn v. Scranton
City,
We also conclude that the statutes involved do not offend the Fourteenth Amendment to the United States Constitution. In
Allied Stores of Ohio, Inc. v. Bowers,
Finally, tlie action of the lower court in refusing certain individual taxpayers the right to intervene in this action is assigned as error. In view of our conclusions as enunciated in the foregoing opinion, we feel it is unnecessary to discuss the merits of this question.
The order of the lower court is affirmed with modification. The record is remanded to permit the lower court to enter a final order consonant with this opinion. Mr. Justice Cohen dissents.
