Holmes notes that
Some method of detecting the effects of a potion must be found. If the characters lack a detect magic spell, they may dare a tiny sip to see what the result may be. This would leave enough potion to accomplish its complete effect.This is an interesting passage. First, it suggests that detect magic could be used to identify the type of potion, although it's admittedly far from clear on that point. Second, it states that one might be able to take a sip to identify a potion, presumably with its effects, whatever they may be, lasting only briefly. It's funny because, back when I first used Holmes, we interpreted this latter point by giving each type of potion a distinctive taste, so that, with time and careful records, one could learn that, for example, a strawberry flavored liquid was a potion of healing, while a cherry flavored one was a potion of haste.
As in OD&D, a potion of growth can be drunk multiple times, with the amount of the whole drunk determining how tall a character grows. A potion of diminution, meanwhile, does not work similarly. Holmes's potion of giant strength is more potent than that in OD&D, granting 3d6 bonus damage rather than 2d6. Otherwise, the potions in the Blue Book are like those in the LBBs, except fewer in number.
Scrolls in Holmes are quite distinctive. As in OD&D, they are purely the province of the magic-user, except for protection scrolls. He does not provide any means of determining the spells inscribed on a scroll, suggesting only "some random method," but the LBBs are only slightly more helpful in this regard. Protection scrolls in Holmes are more powerful than in OD&D, affecting the same area (10' radius) but lasting 6 turns for all types and having no limit on how many enemies against whom it is effective, as in the LBBs.
More intriguing is that Holmes scrolls can replicate the effects of "any potion spell except delusion or poison," "any ring spell except wishes or regeneration," and "any wand spell," meaning that, in a campaign that uses these rules, there are scrolls of gaseous form, scrolls of contrariness, and scrolls of fear. There are also scrolls of healing, which would enable a magic-user to cast cure light wounds. Now, it's worth noting that, in Blue Book, there is no means to copy a scroll spell into a spellbook, so, even if a MU finds a scroll of healing, he can't use it to add magical healing to his repertoire. Still, it's an odd thing nonetheless and it does make one wonder both what Dr. Holmes was thinking here and how one explains the existence of such scrolls within the game world. I personally see Holmes's scrolls as an opportunity to "shake things up," reminding players that magic doesn't always play by the rules, but, even so, it's hard to deny that Holmes's approach is an aberration in the history of the game, both without precedent beforehand and never again employed in subsequent editions.