310 



SCIENCE. 



[Vol. X. No. 255 



This wheel H runs along a metallic rim encircling G ; the rim 

 not being continuous, but having small breaks at the points touched 

 by the wheel H when the vane points N E, S E, S W, N W. 

 These breaks are so short that when H, in its revolution around G, 

 leaves one segment of the rim, it almost instantly rests against the 

 next. 



The segment L is connected with the binding-screw of 4, by the 

 wire passing through O. Similarly K is connected with 3, N is 

 <;onnected with 2, and M \% connected with i. 



The wire G F \s in metallic connection with G H, and is also 

 ■connected with the free pole of the battery E. 



We will now suppose that the anemometer and vane are exposed 

 to the wind, and the wind is from the west. We shall then have 

 the arrangement shown in the diagram. 



The metallic connection C 7 'i K H G F E D B will be complete ; 

 ■and whenever the anemometer closes the circuit B C, the armature 

 R' will be attracted by the double coil magnet 3 7. So, for any 

 winds between 5 W and N IV, the armature li' will indicate each 

 mile or kilometre of wind. Similarly the armatures 7?, 7?", Ji'" will 

 •indicate northerly, southerly, or easterly winds. 



By attaching recording pencils to the armatures 7i, R', R" , R.'" 

 ■and allowing a chronograph sheet to pass beneath them, we can 

 register in separate columns the amount of wind from the four 

 points. By doubling the number of segments, electro-magnets, and 

 recording pencils, the velocities can be recorded for eight points of 

 -compass. 



The recording pencils can be made to register their marks in 

 ■lines running side by side and parallel, and within narrow limits, by 

 bending the pencil-holders attached to the armatures in such a 

 manner as to bring the pencil-points close together, and into an 

 alignment transverse to the motion of the recording sheet. 



In readmg the record sheet, the sums of the registrations in the 

 separate columns will give directly the amount of wind blowing 

 from the different quarters. 



So far as the apparatus for wind, direction, and velocity is con- 

 cerned, the method that I have here described is applicable to most 

 of the electrical registering anemoscopes and anemometers now in 

 use, with very little change ; but the registering apparatus (chrono- 

 graphs, pencils, electro-magnets, etc.) will require more alteration, 

 especially for the American form of cylinder chronograph. The 

 European chronographs, with the long narrow paper strips for 

 recording sheets, will answer the purpose very well, and they 

 are usually of much better construction than the cheaper American 

 chronographs. 



In actual practice a single wire connecting C 5 6 7 8 would be 

 used in place of the four wires shown in the diagram (C5, C6, C7, 

 C8). 



It might perhaps also be found best to make a continuous 

 record of the wind direction by means of a cylinder encircling the 

 rod G with a sliding pencil, the motion of this last being regulated 

 by the chronograph clock-work. Frank Waldo. 



Cincinnati, O., Dec. id. 



American Microscopes. 



The complaint which Dr. Minot makes in a recent number of 

 Science (x. No. 252) about the tendency of American microscope- 

 makers to furnish instruments which are much more decorative 

 than useful, and which are seriously lacking in the optical excel- 

 lence which the genuine scientific worker requires, expresses, I 

 think, the feeling of every one who is frequently called upon to pur- 

 chase microscopes, or advise about their construction. 



It seems to me, however, a matter for regret that Dr. Minot, 

 through inadvertence, I feel sure, should have made so sweeping 

 and indiscriminate a condemnation of all American microscopes, 

 I think that he must have been unaware of the excellent instru- 

 ments which have been furnished of late from the workshop of J. 

 Grunow in New York. 



The useless and positively objectionable features which Dr. 

 Minot so justly attributes to the American microscope in general, 

 are absent from these new forms of stand, while the requirements 

 which he so admirably summarizes are just those which Mr. 

 Grunow has succeeded in covering. 



A firm base ; low, large solid stage, with simple clips for the 

 slide; excellent brass-work ; with or without knee, nose-piece, and 

 rack and pinion, coarse adjustment, Abbd condenser, as the pur- 

 chaser may desire; and optical qualities in the lenses which bring 

 them strictly within the category of first-class, — these are the 

 qualities which the new Grunow instruments present. Forty of 

 these microscopes have recently been added to the supply of the 

 laboratory of the Alumni Association of the College of Physicians 

 and Surgeons, New York, after a full personal examination of in- 

 struments supplied by the more prominent continental makers. 



I feel greatly indebted to Dr. Minot for clearly indicating, as 

 only an accomplished microscopist like himself could, the direction 

 in which American microscope-makers should work, and I am cer- 

 tain that he will learn with pleasure that by one American maker 

 at least, his requirements are being scrupulously met. 



T. Mitchell Prudden. 



New York, Dec. 12. 



The issue of Science of Dec. 2 contained an article which is so 

 sweeping in its denunciation " of any microscopes whatsoever of 

 American manufacture," and its commendation of the German or 

 French instruments, and places the motives of American manufac- 

 turers in such questionable light, that as one of them, and especially 

 in consideration of circumstances hereinafter mentioned, I con- 

 sider it proper to say something in answer. 



The objections in the article can be enumerated as follows : — 



1. " The fundamental error in microscopes of American manu- 

 facture is that they are for the most part constructed with a view 

 of, I might almost say, entrapping inexperienced purchasers. The 

 zeal of the maker is turned too much to decorative lacquering and 

 nickel-plating ; he adds to his stands as great a variety of mechani- 

 cal contrivances and adjustments as the price of the stand will 

 permit, and many of these contrivances are not really commendable 

 for their utility." 



The supply of a product is created and controlled by the demand 

 for it. As the microscope is an instrument for scientific research, 

 it is used by a class of people of more than ordinary intelligence ; 

 and, as most of the instruments purchased pass through the hands 

 of persons of wide experience, they are fully capable of determin- 

 ing what is best suited to their wants, and will certainly not permit 

 the maker to prescribe what they should take. The American in- 

 struments as constructed to-day are almost generally a combina- 

 tion of improvements, such as have suggested themselves to the 

 practical mind of the advanced American worker, and which have 

 been adopted and carried out by the maker ; and this co-operation 

 between worker and maker has long been a matter of congratula- 

 tion. That the majority of American innovations are real improve- 

 ments is shown by the fact that the need of them is felt abroad, 

 and that many of them are being gradually embodied into foreign 

 instruments. That the American maker "adds to his stands as 

 great a variety of mechanical contrivances and adjustments as the 

 price will permit," is certainly not to his discredit, neither is the 

 fact that he endeavors to make the outward appearance of his in- 

 struments conform to that of its general workmanship. 



2. " In the majority of cases the stands are made to tilt, which, 

 for one that uses the microscope for real work, is an almost useless 

 luxury." 



Whether an instrument shall be used in an upright or inclined 

 position depends upon the requirements of the worker. It is true 

 that " in the majority of cases the stands are made to tilt; " but as 

 this feature adds, not a considerable, but, on the contrary, a very 

 trifling expense, there is no reason why it should not be used con- 

 tinually in an upright position if so desired ; and it gives the ad- 

 ditional advantage that it may be inclined, and there is no doubt 

 that much real work is accomplished when it is in this position. 

 However, instruments without the joint are catalogued by some 

 makers, and may be had by those who desire them ; but the fact 

 that the maximum ratio of instruments without joint, as against 

 those with them, is as i to 100, is sufficient evidence of the desir- 

 ability and inexpensiveness of the hinge. 



3. ".This same fact . . . renders it indispensable that the micro- 

 scope should not be too high, ... so that we must put down the 

 ten-inch tube as a bad feature for a student's microscope." 



