The opinion
Holmes, J.,
concurring in part and dissenting in part. I concur generally in the majority opinion, but dissent from the conclusion that the battery charging equipment would not be tax exempt. These electrical units should be exempt in that they are an integral part of the electric mobile units. Without power the latter could not operate to transport the materials, indeed becoming immobile mobile units. Being an integral part of the transporting units, the chargers should be afforded the same tax treatment of exemption.